Volume 5 biomass and biofuel production 5 09 – life cycle analysis perspective on greenhouse gas savings

Volume 5 biomass and biofuel production 5 09 – life cycle analysis perspective on greenhouse gas savings Volume 5 biomass and biofuel production 5 09 – life cycle analysis perspective on greenhouse gas savings Volume 5 biomass and biofuel production 5 09 – life cycle analysis perspective on greenhouse gas savings Volume 5 biomass and biofuel production 5 09 – life cycle analysis perspective on greenhouse gas savings Volume 5 biomass and biofuel production 5 09 – life cycle analysis perspective on greenhouse gas savings

N Mortimer, North Energy Associates Ltd, Sheffield, UK

© 2012 Elsevier Ltd All rights reserved

5.09.1 Biofuel Potential

in various forms, that can be used to generate heat and/or electricity In this context, only biofuels that are produced for transport applications will be considered here Biofuels include bioethanol and biobutanol, which are possible replacements for petrol or gasoline, and biodiesel and synthetic diesel, or syndiesel, which can be used in place of diesel fuel, diesel engine road vehicle (DERV) fuel, marine fuels, and aviation fuels These are liquid fuels but methane-rich gas can also be produced from biomass feedstocks, in the form of biogas, biomethane, or biosynthetic natural gas (bioSNG), as an alternative to conventional fuels in modified versions of existing vehicles, usually for road transport

One common feature of these biofuels is that they contain, totally or partially, carbon, which has been derived from biogenic

feedstocks for use in a variety of applications, including transport, by means of modified internal combustion engines or fuel cells

can also be regarded as a biofuel

Comprehensive Renewable Energy, Volume 5 doi:10.1016/B978-0-08-087872-0.00510-2 109

Biofuels can be produced from an extremely large and diverse range of biomass feedstocks by means of a number of different processing technologies Some of these technologies, such as fermentation, are well established and, indeed, quite old Other technologies are very new and are currently the subject of research and development The enduring attraction of biofuels as major sources of energy is due to their prospective benefits:

• they can potentially provide alternative sources of transport fuel, which can be used in existing vehicles without major modification;

• they can be derived from many diverse, potentially renewable sources of energy;

• they can potentially reduce dependence on crude oil, thereby contributing to national or regional energy security and assisting the transition away from depletable energy resources; and

• crucially, they can potentially reduce GHG emissions, which are responsible for global climate change

It is in this last regard that the attraction of biofuels has been most strongly recognized Total GHG emissions from transport are rising globally and this trend is expected to be maintained into the foreseeable future unless significant, practical means can be found to eliminate or reduce such emissions while ensuring access to sustainable mobility However, achieving this is a very substantial challenge Most analysts and policy makers realize that there is no single means of addressing this challenge, especially within the relatively short timescales required Biofuels have been seen by many as one possible option that, in combination with other solutions, can be implemented relatively quickly to initiate the urgently needed move toward sustain­able mobility

during their production and/or combustion, by growth of succeeding biomass feedstocks However, it has long been realized that GHG emissions are associated with the cultivation or provision of biomass feedstocks and their conversion into suitable biofuels

chain For certain biofuels under specific circumstances, these associated GHG emissions can be very significant In particularly extreme cases, more GHG emissions can be released during the production of a biofuel than those emitted in the production and use of the conventional transport fuels that they are intended to replace Clearly, from the perspective of global climate change mitigation, it is imperative to avoid such undesirable and unintended outcomes Consequently, assessment of total GHG emissions associated with biofuels has become a fundamentally important consideration for their development and deployment as well as for the policy and regulatory frameworks that promote their production and utilization

5.09.2 Life Cycle Assessment

The fundamental basis for determining the relative benefits or disbenefits of biofuels is life cycle assessment (LCA) This is a well-established technique for evaluating the total natural resource and environmental impacts of a product or service over its defined life cycle The basic principles of LCA are documented within International Organization for Standardization (ISO) 14040

service is not a trivial task since a very considerable amount of information is required in a full LCA study Apart from demanding data requirements, uncertainties can arise due to lack of complete scientific knowledge of some environmental pathways that connect emissions to impacts These and other considerations qualify the results of LCA as a means of informing decisions by policy makers on sustainable development Despite possible limitations, LCA finds ever-increased application in the specific evaluation of total GHG emissions as the need for effective mitigation measures grows in response to global climate change

Although LCA principles are well known, their specific application in practice is open to a necessary degree of interpretation This enables subsequent results to address, appropriately, the different specific questions to which LCA studies can be applied For this reason, numerous evaluation procedures and computer-based tools, based on different calculation methodologies, are available In terms of evaluating total GHG emissions associated with biofuels, differences between calculation methodologies focus mainly on the following issues:

• Systems boundary This is an imaginary line drawn around the process under consideration which specifies the extent of analysis of GHG emissions along and beyond the main process chain associated with the production of a biofuel For example, the systems boundary will establish whether GHG emissions related to the manufacture, maintenance, and decommissioning of plant, machinery, and equipment are included in or excluded from calculations

• Reference system This relates to whether any account is taken of the GHG emissions effects of the potential alternative use of a main resource input or inputs to the production of a biofuel For example, GHG emissions may be avoided or increased when land is used to cultivate biomass feedstocks or when disposal is avoided by using wastes in biofuel production

• Coproduct allocation This is a procedure that is required when more than one product is produced by a process For example, it is the stated means by which the total GHG emissions of production are, in effect, attributed to or otherwise divided between a biofuel, as the main product, and by-products, such as animal feed

• Surplus electricity Sometimes, surplus electricity is available for sale from biofuel production processes that use combined heat and power (CHP) units, and this has to be accounted within the GHG calculations This is sometimes achieved by subtracting a given amount of GHG emissions, derived using stated assumptions, that are effectively avoided when this electricity displaces electricity from another source

Specific GHG calculation methodologies and tools adopt different approaches to these and other issues A summary of the main

evaluating GHG emissions for biofuels during the introduction of the Renewable Transport Fuel Obligation (RTFO) in the United

a more broadly applicable approach is offered by the British Standards Institution (BSI) Publicly Available Specification 2050 (PAS

of total GHG emissions of biomass energy technologies, generally, and biofuels, specifically, the Biomass Environmental

expanding use of biofuels

The existence of different methodologies and tools and, more crucially, the derivation of clearly different results for apparently the same biofuel have generated much confusion, debate, and controversy There are often numerous reasons for differences in results, in the form of total GHG emissions Sometimes, this involves differences in important assumptions and/or values for key parameters that have not been openly stated and emphasized This can be resolved quite easily by ensuring adequate transparency in calculations as a fundamental principle at the heart of any meaningful evaluation that is expected to engender confidence However,

a more widespread cause of discrepancies is the adoption of different approaches to the calculation of total GHG emissions Unfortunately, the justification of a chosen approach is sometimes not explained comprehensively and explicitly This can give the

Table 1 Summary of the main differences of a selection of GHG emission calculation methodologies and tools

Systems

boundary:

plant,

equipment,

and Reference system: Reference system: Coproduct

Methodology machinery land use waste disposal allocation Surplus electricity

RFA Excluded Not taken into account Not taken into Substitution credits Avoided GHG emissions based Technical

Guidance

[3]

possible with price allocation otherwise

on marginal electricity generationa

Waste products and residues assumed provided without GHG emissions Taken into account

in comparisons

Energy content allocation

Price allocation chiefly with substitution credits for

Avoided GHG emissions based

on generation of electricity using the same fuel as CHP unit in conventional plantb

Avoided GHG emissions based

on displaced average grid electricityc

BEAT2 [6] Included Assumes maintained

fallow set-aside where relevant

Landfill with energy recovery where relevant

electricity surpluses Price allocation unless substitution credits possible and significant

Avoided GHG emissions based

on displaced net grid electricityd

a

b

c

d

impression that such choices are arbitrary and ignore the essential requirement of any given application of LCA that it must state and address the particular question it seeks to answer This is not a trivial or academic issue since the rules chosen in GHG emissions calculations can have a very fundamental influence over subsequent results, their interpretation, and their meaningful comparison Before examining some of the details of differences in approaches, it is instructive to set this discussion in the context of the purposes behind the calculation of total GHG emissions Although the principles of LCA emphasize the need to adopt the correct approach that actually answers the specific question being asked, it is often not immediately apparent what this means in practice This is usually because the specific question under consideration is not stated or clarified sufficiently There is ongoing deliberation about this in the general field of LCA among academics and practitioners However, it has been the debate over biofuels, and whether or not they reduce overall GHG emissions, that has begun to draw out the basic foundations on which choices between different calculation methodologies should be made

In this regard, there are important distinctions between types of LCA, which, in particular, include consequential LCA and

new product or new activity Hence, consequential LCA tends to be an ex ante approach that is specifically relevant to policy analysts

This involves tracing and quantifying all the implications, and their relevant connections, that have been induced by policies that support new products or activities This is frequently much more challenging than might be imagined as it can require the detailed modeling of consequences on a truly global scale Such modeling can often be highly demanding in terms of data requirements, which far exceed existing capabilities

In contrast, the purpose of attributional LCA is to allocate total GHG emissions to a specific product or service This evokes the

can be seen that attributional LCA is most suitable for ex post evaluation of a product or service that is specifically relevant to regulation

practicalities of decision making by those who are directly involved with the provision of a product or service In the parlance of

financial aspect Hence, it can be argued that, in the regulatory context, GHG emissions should be attributed on an economic basis Consequential and attributional LCA have very different purposes, involve very different approaches, and usually produce quite different results Both are valid in terms of the specific questions they seek to answer However, the basic foundations that they provide have rarely been adopted with necessary rigor in the development of existing, official methodological frameworks or most

emissions for biofuels that should be adopted for strict compliance with the purposes and logic of these types of LCA By comparing Tables 1 and 2, it can be seen that existing methodologies and tools are not completely suitable for either policy analysis or regulation

Among the many differences between calculation methodologies and tools is the treatment of coproduct allocation Such allocation procedures are important because by-products are often generated during the production of prominent biofuels and should, therefore, carry part of the GHG emissions burden associated with the biofuel production process A variety of coproduct allocation procedures can be adopted including the use of substitution credits and allocation by energy content and price The use of substitution credits first involves calculating the total GHG emissions for the entire process chain Then, GHG emissions that would have been associated with the normal generation of alternative products which are displaced by the by-products of biofuel production are subtracted from this total As such, this is an accounting procedure rather than strict allocation Additionally, in order to determine the substitution credit, it is necessary to identify the displaced product and evaluate the total GHG emissions

Table 2 Summary of aspects of calculation methodologies for compliance with consequential and attributional LCA

Reference Systems boundary: Reference system:

Suitable plant, equipment, and system: land waste Coproduct Surplus Type of LCA and question answered application machinery use disposal allocation electricity Consequential LCA: What are the Policy Included Taken into Taken into Substitution Substitution complete GHG emissions impacts of analysis account account credits creditsa

introducing a new policy?

Attributional LCA: Who is responsible Regulation Excluded Possibly not Possibly not Price Price

accountb accountb

a

b

c

associated with its production Apart from this extra analysis, which is, in effect, the result of expanding the systems boundary, it should be noted that substitution credits can vary over time as displaced products and their means of production change Allocation by energy content, price, or other characteristic attribute simply involves dividing the total GHG emissions for a process between coproducts on an effective percentage basis The energy content of a product is a fixed characteristic and allocation is performed by forming percentages based on the energy content (calorific or heating value) of each coproduct multiplied by their respective masses Unless technical conditions alter, such allocation does not change with time because the data involved consist of the physical properties of the coproducts However, the choice of energy content allocation is rarely explained or justified and, indeed, any physical characteristic could have been selected as a basis for allocation While it is sometimes suggested that the choice of energy content allocation reflects the fact that coproducts could be burnt for energy generation, it is quite clear that, in most instances, this does not happen Furthermore, some coproducts may not have an energy content and, in such cases, this allocation procedure would not be appropriate Similar criticisms apply to the choice of other physical properties, even mass, which is occasionally used, but is also not universally suitable since it fails to accommodate the generation and sale of electricity as a coproduct

Allocation by price involves multiplying the amount of each coproduct by its respective price to determine percentage contribu­tions to total economic value as a basis for dividing total GHG emissions The main justification for using price allocation is that it, in effect, assigns responsibility for GHG emissions in line with financial benefits The most obvious drawback of this allocation procedure is that it varies over time in response to changes in the relative prices of coproducts Additionally, some coproducts may

uncertainty into the calculations It can also be argued that, even where market prices are available and known, they may not

indicator of financial worth to the economic operator Finally, commercial companies may prefer to avoid using price allocation because it could reveal financially sensitive data if such information has to be revealed to a third party in the regulatory process Regardless of which coproduct allocation procedure is adopted, it is apparent that most existing calculation procedures and tools

forms which mix specific approaches together in a fairly arbitrary way Only the EC Renewable Energy Directive appears to apply

a single coproduct allocation procedure However, it could be argued that special treatment of surplus electricity, which, after all, is

a by-product, introduces a degree of inconsistency even in this calculation methodology Another potential source of discrepancy is the approach adopted for waste products that are used to produce some biofuels In particular, it is assumed that no actual or avoided GHG emissions are associated with the provision of these biomass feedstocks This may not reflect what happens in practice and it

It should be apparent from this brief discussion of some of the details of GHG calculation methodologies and tools that there are fundamental differences, which will ultimately lead to differences in the final results This is unfortunate because it can create confusion and mistrust in the results of GHG emission calculations Hence, the basis of calculations, including their intended purpose, should always be clearly stated so that subsequent users can understand what may be causing differences between published results It also needs to be appreciated that calculation methodologies and tools can produce a wide variety of forms

(GWPs) Ideally, the values of the GWPs used should also be stated since these can vary depending on the time period under consideration and their original source Normally, a 100-year time horizon is chosen and relevant values are taken from the

the combination of GWPs adopted by selected methodologies and tools

To simplify the presentation of results and the establishment of targets, net GHG emissions savings are often quoted and these will be used predominantly here (the current target for biofuels used in the European Union is for net GHG emissions savings of at least 35%, increasing to 50% by 1 January 2017 for existing biofuel plants and to 60% for new biofuel plants that start production

Table 3 Global warming potentials for methane and nitrous oxide (100-year time horizon)

Global warming potential

Source of data

Methane (kg eq CO2 kg−1 CH4)

Nitrous oxide (kg eq CO2 kg−1 N2O) Adoption by methodology or tool Second Assessment Report [9]

Third Assessment Report [10]

Fourth Assessment Report [11]

RFA Technical Guidance [3]

EC Renewable Energy Directive [4]a

Table 4 Examples of current baseline values of total greenhouse gas emissions for conventional fuels

Total greenhouse gas emissions (kg eq CO2 MJ −1)

RFA Technical Guidance [3]

EC Renewable Energy Directive [4]

0.0848 0.0838

0.0864 0.0838 DERV, diesel engine road vehicle

associated with biofuel production and the total GHG emissions of production and use of the conventional fuels (petrol/gasoline, diesel/DERV, etc.) that they displace The relevant expression for this is given as follows:

In order to determine net GHG emissions savings, it is necessary to have baseline values for the total GHG emissions associated with the production and use of conventional fuels Examples of the baseline values for petrol and diesel currently recommended in

EC values are adopted here in the derivation of net GHG emissions savings

Given the diversity of factors that can affect the evaluation of net GHG emissions savings of biofuels, a single accessible tool for

manufacture, maintenance, and decommissioning of plant, machinery, and equipment; assuming that no GHG emissions are associated with the use of waste and residues for biofuel production; coproduct allocation is based on energy content; avoided GHG emissions of surplus electricity are based on those of electricity generated by conventional means from the same fuel as used in CHP

5.09.3 Net Energy Balances for Biofuels

The assessment of the prospective benefits, or otherwise, of biofuels has a long history and has often attracted controversy This goes back to the 1970s, at least, when a number of studies were conducted in the United States on the net energy balances of bioethanol

fuel sources, than would be available from bioethanol (net energy balance >1) It became apparent that assumptions about the source of heat and electricity used in proposed US bioethanol plants was a crucial consideration in the net energy balance Indeed, it was suggested that the possible use of agricultural residues, in the form of corn stover, could result in net energy balances in which

More recent studies have revisited this issue and found that current US bioethanol production from maize, based predominantly

on the use of coal as a source of energy in processing, has a net energy balance greater than unity, as well as unfavorable

this conclusion in its proper context of the US biofuel policy, which has fostered recent bioethanol production in the United States This was motivated by an intention to reduce foreign oil imports and to support agriculture rather than by action to avoid fossil fuel resource depletion and to mitigate global climate change It could be argued that this policy has been successful in its intended purpose of, in effect, turning US coal into bioethanol as an alternative to petrol/gasoline derived from imported crude oil There are obvious dangers in drawing broad conclusions from specific cases that are relevant only within particular policy frameworks

A range of different net energy balances are possible depending on the particular biomass feedstock and the details of how it is

which provide estimates of primary energy consumption as well as GHG emissions (It should be noted that, unlike the derivation

of GHG emissions within frameworks such as the RFA Technical Guidance and the EC Renewable Energy Directive, there is no

reference systems for land use were excluded, the manufacture, maintenance, and decommissioning of plant, equipment, and machinery were included (although these contributions are often excluded from GHG emissions calculations), and primary energy substitution credits were used for coproducts (animal feed and surplus electricity from CHP).) In this context, primary energy is the energy available from fossil and nuclear fuels, and, as such, is a measure of energy resource depletion The net energy balance can be found by dividing the primary energy consumption of biofuel production by the delivered energy, or energy content, of the biofuel

0.31 0.41 0.31

1.20 1.26

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Net energy balance (MJ MJ−1)

Figure 1 Net energy balances for examples of bioethanol production Notes: (a) Assuming mainly processing by coal-fired boilers and grid electricity [18] (b) Simulated using BEAT2 [6] with a substitution credit of 7.967 MJ kg−1 protein for animal feed [18] (c) Simulated using BEAT2 [6] with a substitution credit of 7.967 MJ kg−1 protein for animal feed [18] and a substitution credit for US grid electricity of 2.540 MJ MJ−1 [19] displaced by surplus electricity from the combined heat and power unit (d) Simulated using BEAT2 [6] with a substitution credit of 7.967 MJ kg−1 protein for animal feed [18] and a substitution credit for UK electricity of 2.952 MJ MJ−1 [20] displaced by surplus electricity from the combined heat and power unit

coal-fired boiler with imported grid electricity is used for bioethanol production from US maize/corn, net energy balances are greater than unity However, a net energy balance of less than unity arises if it is assumed that a natural gas-fired CHP unit supplies all the heat and electricity requirements of the bioethanol plant Other examples of bioethanol production that produce favorable

5.09.4 Greenhouse Gas Emissions Results

As with net energy balances, estimated net GHG emissions savings of the production and use of biofuels depend on many factors

presents typical values for net GHG emissions savings for current biofuels (biodiesel, bioethanol, and biogas) as quoted in the EC

In general, estimated net GHG emissions savings from these two sources are similar, as will be shown shortly For the time being, a

can be achieved with biodiesel derived from recycled vegetable oil and biogas from dry and wet manure Much lower net GHG

effluent from oil mills, resulting in large contributions to total GHG emissions Such emissions can be reduced significantly by

growth) or using it as a supplementary energy source in the mill The improvement in net GHG emissions savings, from 36% to

modest net GHG emissions savings (32%) while these can be increased markedly (69%) by using a straw-fired CHP unit Of all the liquid biofuels derived from cultivated biomass feedstocks, the highest net GHG emissions savings are realized by bioethanol

GHG emissions savings can depend on the specific details of biomass feedstock provision and processing

The origins of some differences between net GHG emissions savings for particular biofuels can be suggested by examining

from UK oilseed rape (56%) and French sunflowers (40%) and for bioethanol produced from UK wheat grain (63%), US maize/ corn (54%), and sugarcane (42%) (It should be noted that relative contributions to total GHG emissions can be affected by the

production from US soybean is high (63%) because nitrogen (N) fertilizer application rates are low and the contribution from

Biodiesel from oilseed rape; UK (a)

Biodiesel from sunflowers; France (a)

Biodiesel from soybean; USA (a)

Biodiesel from oil palm; Malaysia (b)

Biodiesel from recycled vegetable oil; UK (c)

Bioethanol from sugar beet; UK (a)

Bioethanol from wheat grain; UK (a)

Bioethanol from maize/corn; USA (a)

Bioethanol from sugarcane; Brazil (d)

Biodiesel from oilseed rape Biodiesel from sunflowers Biodiesel from soybean Biodiesel from oil palm (without methane capture)

Biodiesel from oil palm (with methane capture)

Biodiesel from recycled vegetable oil

Bioethanol from sugar beet Bioethanol from wheat grain (lignite-fired combined

heat and power) Bioethanol from wheat grain (natural gas-fired boiler

and grid electricity) Bioethanol from wheat grain (natural gas-fired

combined heat and power) Bioethanol from wheat grain (straw-fired combined

heat and power) Bioethanol from maize/corn (EU natural gas-fired

combined heat and power)

Bioethanol from sugarcane Biogas from wet manure Biogas from dry manure

processing (oil extraction, refining, and esterification) is relatively low Relative contributions from processing are high for biodiesel

vegetable oil, because all other contributions are small It should be noted that in all cases where CHP units are used in processing, the estimated contribution from processing includes deduction of avoided GHG emissions from the sale of surplus electricity

distribution are relatively minor The main exception to this is bioethanol production from Brazilian sugarcane where transport distances are assumed to be comparatively higher than in biofuels produced in other countries

Among the many factors that can affect estimates of net GHG emissions savings of biofuels, the most prominent are

• consideration of systems boundaries, in particular, direct (dLUC) and indirect (iLUC) land use change;

emissions from soil;

• source of processing energy, as related to specific fuels used to provide heat and electricity for biomass feedstock conversion to biofuels;

• methods of GHG emissions calculation, mainly as affected by the choice of coproduct allocation procedures;

• nature of biomass feedstocks, specifically, differences between cultivated crops and waste products;

• treatment of reference systems, with regard to accounting or otherwise of avoided GHG emissions; and

• advances in biofuel production, as represented by future technologies

The effects of all these important factors are examined and discussed in the remainder of this chapter, with illustrations by means of

5.09.5 Land Use Change

Arguably the most controversial and problematic issue for the global climate change mitigation potential of biofuels concerns land use change This is because potential GHG emissions from land use change can eliminate any estimated benefits of biofuels or, indeed, make them worse than conventional transport fuels even without taking account of the GHG emissions from the rest of the production process or chain Land is a major constraining factor in the production of any biofuel that is derived from cultivated crops Dependence

on cultivation has, of course, the attractive feature that it enables the amount of biofuels that can be produced, on a regular (mainly annual) basis, to be predetermined and, if necessary, varied or, specifically, increased, to a certain degree Depending on the mechanism by which biofuel demand translates into biomass feedstock supply, various levels of production can be planned and controlled This contrasts with the production of biofuels from waste products, including agricultural, forestry, and arboricultural residues, the ultimate availability of which depends on other factors that cannot be varied at will as they usually depend on other, separate considerations In particular, the normal economic mechanism by which increases in price bring forward supply does not operate completely with respect to wastes and residues In the short term, such sources of biomass feedstocks are fixed whereas

Despite this attractive feature, cultivated biomass feedstocks are affected by a potentially major negative implication because the land on which they are grown could be used for other purposes Obviously, there is competition over land between biomass feedstocks and crops for food, materials, and other purposes There is also possible conflict over land for completely different uses including urban and infrastructure development As discussed previously, alternative land use is normally addressed in LCA studies

by means of reference systems, which, in effect, expand the systems boundaries applied to the activities under consideration However, evaluation of the effects on GHG emissions calculations can be extremely complicated and can have far-reaching consequences as it is necessary to account for the actual changes to any given area of land and, potentially, its subsequent impact

on global land use Such analysis is not trivial and final impacts may be large or small, depending on circumstances and assumptions Overall, consideration of land use change can introduce considerable uncertainties into the assessment of net GHG emissions savings for biofuels

5.09.6 Direct Land Use Change

Of the two broad types of land use change, dLUC is more easy to accommodate with regard to estimating total GHG emissions associated with biofuels The issue of dLUC arises when land is converted specifically for the cultivation of biomass feedstocks for

the default setting is that land for growing oilseed rape, sugar beet, wheat grain, etc., was previously maintained set-aside that had been withdrawn from agricultural production due to EC policy measures Typically, this land is assumed to be fallow and mown

relatively low emissions are, effectively, avoided by cultivating such land for biofuels so they constitute a negative net emission, or a

‘credit’ in the GHG emissions calculations for the subsequent biofuel However, because of changes in EC agricultural policy, such land designation has disappeared over a period of time Hence, this adjustment in calculations is now less meaningful

biofuels This is because, in response to existing policy measures and targets that will increase pressure for biofuel production, land will need to be found for biomass feedstock cultivation While some of this will be current food cropland, which will generate other problems (see below), it may also be necessary to convert other forms of land to biomass feedstock cultivation This may include

certain categories of land, such as grassland, woodland, peatland, and wetland, which may be available in relatively large areas and may be considered to have a low economic value, in narrowly defined terms Leaving aside other important environmental impacts, such as the loss of habitat and reduction in biodiversity, the conversion of such land can present significant issues for GHG emission calculations Depending on the specific nature of this land and how it is converted to cultivation, substantial quantities of GHGs can

especially in terms of allocation to subsequent cultivated crops Additionally, foregone opportunities to sequester carbon by this land in its previous form have to be considered, although this may be partially counterbalanced by the carbon sequestration potential of certain biomass feedstocks

In the United Kingdom, the possible implications of dLUC on GHG emissions associated with biofuel production were

conversion of certain types of land, especially grassland, to biomass feedstock cultivation for current biofuel production It was apparent from the Gallagher Review that a systematic and comprehensive approach would need to account for all possible land use conversion to all types of biomass feedstock Such an approach is now available in the form of EC Guidelines for the calculation of

the carbon stock of the soil and vegetation (above- and below-ground) before and after conversion to biomass feedstock cultivation This takes into account the climate region, soil type, land management factors which are intended to reflect type of land use, degree

of tillage and level of organic inputs, and the nature of the vegetation Default values for these factors are based on IPCC data supplemented with data specific to the cultivation of relevant biomass feedstocks for current biofuel production To assist application, global maps of climate regions and soil types are also provided The resulting net carbon stock change per unit area

The effect of such net carbon stock changes resulting from dLUC on net GHG emissions savings varies depending on circumstances, particularly in terms of the biomass feedstock yield, which is related to the specific biofuel, and the original land

wheat cultivation for bioethanol production and Malaysian forest/scrubland to oil palm cultivation for biodiesel production Figure 4 compares the net GHG emissions savings of 56% for bioethanol from UK wheat grain without dLUC with savings

Bioethanol from UK wheat grain-conversion from

improved, high-input grassland (a, f)

Bioethanol from UK wheat grain-conversion from improved, medium-input grassland (a, e)

Bioethanol from UK wheat grain-conversion from marginally managed, medium-input grassland (a, d)

Bioethanol from UK wheat grain-conversion from moderately degraded, medium-input grassland (a, c)

Bioethanol from UK wheat grain-conversion from severely degraded, medium-input grassland (a, b)

Bioethanol from UK wheat grain-no direct land use

change (a)

Net greenhouse gas emissions savings (%) Figure 4 Net greenhouse gas emissions savings for bioethanol from UK wheat grain with direct land use change Notes: (a) Simulated using modified BEAT2 workbook [6] for bioethanol from wheat grain with a yield of 8.00 t ha−1a−1 at 20% moisture content, processing with a natural gas-fired combined heat and power unit, bioethanol productivity of 62 617 MJ ha−1a−1 and 56.3% coproduct allocation to bioethanol (b) Estimated net carbon stock change

of 73.3–65.5 = 7.8 t C ha−1 [25] for conversion of severely degraded, medium-input grassland to full-tillage, medium-input cropland on high-activity clay soils in a cool, temperate, moist/wet climate (c) Estimated net carbon stock change of 97.0–65.5 = 31.5 t C ha−1 [25] for conversion of moderately degraded, medium-input grassland to full-tillage, medium-input cropland on high-activity clay soils in a cool, temperate, moist/wet climate (d) Estimated net carbon stock change of 101.8–65.5 = 36.3 t C ha−1 [25] for conversion of marginally managed, medium-input grassland to full-tillage, medium-input cropland on high-activity clay soils in a cool, temperate, moist/wet climate (e) Estimated net carbon stock change of 101.8–65.5 = 36.3 t C ha−1 [25] for conversion of marginally managed, medium-input grassland to full-tillage, medium-input cropland on high-activity clay soils in a cool, temperate, moist/ wet climate (f) Estimated net carbon stock change of 127.0–65.5 = 61.5 t C ha−1 [25] for conversion of improved, high-input grassland to full-tillage, medium-input cropland on high-activity clay soils in a cool, temperate, moist/wet climate

Biodiesel from Malaysian oil palm-conversion from Asian

insular native deciduous forest with > 30% canopy cover (a, f)

Biodiesel from Malaysian oil palm-conversion from Asian

insular deciduous forest with > 30% canopy cover, and with

shifting cultivation and mature fallow (a, e)

Biodiesel from Malaysian oil palm-conversion from Asian

insular deciduous forest with > 30% canopy cover, and with

shifting cultivation and shortened fallow (a, d)

Biodiesel from Malaysian oil palm-no direct land use change

(a)

Biodiesel from Malaysian oil palm-conversion from Asian

insular tropical scrubland (a, b)

Biodiesel from Malaysian oil palm-conversion of Asian

insular tropical moist forest with between 10% and 30% canopy

cover (a)

−130−120−110−100 −90 −80 −70 −60 −50 −40 −30 −20 −10 0 10 20 30 40 50 60 70 80 90 100

Net greenhouse gas emissions savings (%) Figure 5 Net greenhouse gas emissions savings for biodiesel from Malaysian oil palms with direct land use change Notes: (a) Simulated using BEAT2-type workbook [14] for biodiesel from oil palm with a yield of 4.08 t ha−1a−1 at 22% oil content, processing with a fuel oil-fired combined heat and power unit and methane capture, biodiesel productivity of 122 708 MJ ha−1a−1 and 31.2% coproduct allocation to biodiesel (b) Estimated net carbon stock change of 81.0–107.0 = –26.0 t C ha−1 [25] for conversion of Asian (insular) tropical moist forest with between 10% and 30% canopy cover to full-tillage, medium-input perennial cultivation on low-activity clay soils in a tropical, moist climate (c) Estimated net carbon stock change of 93.0–107.0 = –14.0 t C ha−1 [25] for conversion of Asian (insular) tropical scrubland to full-tillage, medium-input perennial cultivation on low-activity clay soils in a tropical, moist climate (d) Estimated net carbon stock change of 204.1–107.0 = 97.1 t C ha−1 [25] for conversion of Asian (insular) moist, deciduous forest with greater than 30% canopy cover, and with shifting cultivation and mature fallow, to full-tillage, medium-input perennial cultivation on low-activity clay soils in a tropical, moist climate (e) Estimated net carbon stock change of 211.6–107.0 = 104.6 t C ha−1 [25] for conversion of Asian (insular) moist, deciduous forest with greater than 30% canopy cover, and with shifting cultivation and mature fallow, to full-tillage, medium-input perennial cultivation on low-activity clay soils in a tropical, moist climate (f) Estimated net carbon stock change of 221.0–107.0 = 114.0 t C ha−1 [25] for conversion of Asian (insular) moist, native (nondegraded) or managed deciduous forest with greater than 30% canopy cover to full-tillage, medium-input perennial cultivation on low-activity clay soils in a tropical, moist climate

including the effects of dLUC associated with the conversion of different types of grassland In all instances, the net GHG emissions

these savings are negative, meaning that the bioethanol has higher GHG emissions than petrol derived from conventional crude oil

are other countries where such land may exist

negative net GHG emissions, there are two cases in which savings are higher than the comparative value of 51% for biodiesel production from Malaysian oil palms In these particular instances, consisting of Asian insular moist forest with between 10% and 30% canopy cover and Asian insular tropical scrubland, the carbon stock prior to conversion is lower than that for the oil palm plantation In this regard, the assumed value for the above- and below-ground vegetative carbon content of the biomass feedstock is

a critical consideration However, from such evaluation of the effects of dLUC, it can be seen that there are specific forms of land use conversion that should be avoided if necessary net GHG emissions savings are to be achieved with biofuels Hence, the EC Renewable Energy Directive specifically states that, as part of sustainability criteria, biofuels should not be derived from biomass

particular circumstances depending on the existing carbon stock and the type of biomass feedstock cultivated

In the EC Guidelines for the calculation of carbon stock changes associated with dLUC, it has been assumed that the carbon in

such land clearance However, much of the timber may be recovered for a variety of uses which might, in fact, store carbon for many decades or even centuries Indeed, logging may well be the actual reason for such land clearance, in which case any net CO

emissions should be allocated mainly or wholly to the timber produced rather than exclusively to subsequent crops Regardless of

instances, the reasons for dLUC and its consequences may be complex and interrelated, causing fundamental problems for attributing GHG emissions from land conversion

5.09.7 Indirect Land Use Change

The other form of land use change, which consists of iLUC, is considerably more controversial and potentially more serious for current biofuels in terms of their proclaimed benefits for mitigating global climate change The impact of iLUC on total GHG emissions associated with the production of biofuels is based on the concept of land use displacement With this concept, the cultivation of a biomass feedstock on land that has been previously used to grow another crop will cause the production of this crop

to be displaced elsewhere, which, in turn, may cause yet other crops to be displaced This process of displacement continues until previously uncultivated land has to be converted to agriculture due to global constraints on the availability of such land At this

these emissions depends, crucially, on the nature of the carbon stock that has been disturbed or destroyed If, for example, the

biomass feedstocks for biofuel production

This concept was originally articulated in 2008 when a number of studies were published that attempted to quantify the effect on total GHG emissions associated with biofuels from iLUC Particularly prominent studies concluded that the additional GHG emissions from iLUC were so large that many current biofuels had total GHG emissions greater than those of diesel and petrol

not be able to meet both the targets for biofuel supply and net GHG emissions savings required by the EC Renewable Energy

emissions associated with current biofuels could be large but there were considerable uncertainties about the actual magnitude The basic reason for such uncertainties is the challenge presented by attempting to model land use change globally This requires

an extremely large amount of detailed data for all relevant countries, their land designations, and their existing land use Furthermore, a credible and reliably functioning model of land use displacement effects is needed that can address all the interactions of complex agricultural decision making Since it was apparent by the end of 2010 that neither existing data nor adequate models were available, the EC was unable to resolve the issue of iLUC on GHG emissions for biofuels Instead, the EC set out options that it could adopt in responding to iLUC in 2011 These included taking no action but monitoring developments; increasing the target net GHG emissions savings for biofuels in the EC Renewable Energy Directive; introducing additional sustainability criteria requirements for certain biofuels, which would, in effect, mean that iLUC would be avoided or minimized;

It will be appreciated that the iLUC issue is complex and, possibly, intractable However, it can be argued that, by addressing iLUC in this manner, the EC and similar bodies are attempting to make inappropriate adjustments which conflict with the basis of their regulatory aims As discussed previously, there are clear distinctions between GHG emissions regulation, which needs to be based on attributional LCA, and policy analysis, which has to be based on consequential LCA Practical regulation, in particular, has

ignore the disparity between the attribution of subsequent GHG emissions and the actual ability of economic operators to influence the exceedingly remote consequences of their own actions It could be said that there is a lack of clear thinking about the official methodologies for GHG emissions calculations because they appear to be attempting to address regulation and policy analysis simultaneously Instead, it is essential to accept that these are two quite different purposes based on different types of LCA, which will, by their very nature, generate different results

In the parlance of LCA, the correct and consistent approach depends on where systems boundaries are drawn around the processes under investigation It has to be accepted that, as systems boundaries are expanded to include increasingly remote activities, the level of effective responsibility or ownership of subsequent GHG emissions declines Hence, the establishment of the systems boundary, and its subsequent inclusion or exclusion of GHG emissions, should reflect the ability of the economic operator

to control, directly or indirectly, these emissions In current market situations, this suggests that the systems boundary should be based on economic responsibility Hence, if iLUC is an issue that is caused by global constraints on the availability of agricultural land, this should factor into the economic considerations of those who decide to grow biomass feedstocks through land prices If this link is tenuous, then the effect on GHG emissions for biofuels is weak, and conversely so However, it could also be argued that land prices reflect many influences of which the possible global shortage of agricultural land is just one factor An additional