Biofuels, Solar and Wind as Renewable Energy Systems_Benefits and Risks Episode 2 Part 10 ppt

VV., 2006 pointing out the needfor a production of about 17.5 Mt of biofuels by the year 2010 and the allocation to energy cropping of an agricultural land between 5 and 10 Mha out of th

18.1 Introduction

Two kinds of biofuels are generally considered available and feasible, i.e ethanol and biodiesel, although some expectations are also being placed on futurebio-hydrogen generation Bio-ethanol is obtained through fermentation and distilla-tion of sucrose-producing plants (sugar cane, sugar beet) or cereals (mostly maize),and is usually mixed with petrol, either directly at the pump (splash blends), orbefore distribution (tailor blends) New production methods for bio-ethanol are alsobeing developed, which make use of ligno-cellulosic biomass This is however still

bio-at the R&D stage, and is currently referred to as a “second-generbio-ation” biofuel.The second type of biofuel (named biodiesel or Vegetable Oil Methyl Esters –VOME) is produced from vegetable oils, and the crops that are most widely em-ployed in Europe and in the USA are sunflower, rapeseed (canola) and soy Palmtrees are also a very promising raw material in tropical countries Biodiesel isobtained through a chemical process called trans-esterification, which consists ofmaking the vegetable oil react with methanol, thus yielding biodiesel and glycerine

as co-products, and can only be mixed with fossil diesel

Biofuels raise increasing hopes as substitutes for fossil fuels, and therefore as acontribution towards the reduction of the associated problems of greenhouse effect,high energy expenditures, and energy dependency Moreover, it is often claimed thatbiofuels are not only “green” on a global scale (reducing of greenhouse effect) butalso on a local scale (reducing urban pollution) Finally, biofuels are seen by many

as a motor of rural development

The European Union transportation sector is responsible for about 20% of totalgreenhouse gas emissions (AA VV., 2005) The 2001 European Commission WhitePaper on Tranport Policy (AA VV., 2001) estimated that between 1990 and 2010European CO2 emissions from transportation sector are likely to increase up to 50%,reaching about 1.1 Gt and that road transportation is the main responsible for such

a trend with 84% of total emissions (with minor shares from sea, railway and airtransportation modalities) The same document claimed that “Reducing dependence

on oil from the current level of 98%, by using alternative fuels and improvingthe energy efficiency of modes of transport, is both an ecological necessity and atechnological challenge.” Consistently with these estimates, the European Unionpublished “An EU Strategy for Biofuels” (AA VV., 2006) pointing out the needfor a production of about 17.5 Mt of biofuels by the year 2010 and the allocation

to energy cropping of an agricultural land between 5 and 10 Mha out of the total

140 Mha globally cropped within the EU Member States By the year 2020 thesevalues are expected to double

In the year 2004 the EU biofuel production was 2.4 Mtoe, equal to the 0.8%

of total consumption of liquid fuels within the EU Bioethanol production was 0.5Mtoe and biodiesel production 1.9 Mt Total biomass use for energy within EU isabout 40 Mtoe/year, out of which 18% in Finland, 17% in Sweden, 13% in Austria,2% in Italy In general, biomass use in Europe is still very small, in spite of claimedneeds and expectations

The European Directive 2003/30/EC established that the biofuel share of theenergy use in the transport sector should reach 2% by 2005 and 5.75% by 2010

(EU, 2003) As a consequence, in Italy, the national law No 81 of 11 March 2006(dedicated to urgent norms for agriculture and agro-industry) required all fuel man-ufacturers to release to the market biofuels for at least 1% of the total energy content

of the diesel and petrol sold in the previous year Such percentage must be increased

by one unit per year until the year 2010, in order to reach the 5.75% required by theEuropean Union

The latest European energy strategy, agreed in March 2007, increased the target

to 10% within 2020.1 These targets are quite ambitious considering that the actualbiofuel share of the energy used for transport was only 0.9% in 2005.2Therefore,

in order to get closer to the European requirements, an enormous effort is needed tospur a large-scale biofuel production

In fact, biofuels are not competitive with fossil fuel-derived products if left to thefree market In order to make their price similar to those of petrol and diesel, they need

to be subsidized by three means: (1) European agricultural subsidies, granted throughthe Common Agricultural Policy (CAP); (2) laws requiring a minimum percentage

of biofuels in the fuels sold at the pump (biofuel obligations) and (3) de-fiscalization,since energy taxes make up for approximately half of the traditional fuel price.These three political measures all need financial means, which are provided bythe European Commission (agricultural subsidies), the governments (reduction inenergy revenues), and car drivers (increase in the final fuel price) For this reason,there is compelling urge for an integrated analysis to discuss whether investing publicresources in biofuels (and employing a large extension of agricultural land for that)

is at all an advisable strategy Such analysis should not be limited to energy yield

or economic cost considerations, but also include relevant social and environmentalfactors

In the following sections we will attempt an integrated assessment of the costsand benefits of a large scale biofuel sector in Europe, from environmental, socialand economic points of view, and in the light of the results we will discuss whetherpromoting biofuels is really an advisable strategy The starting point for such anassessment is a case study on biofuel production in Italy, given the present state

of Italian agriculture and land use, from which larger-scale perspectives for Europewill be extrapolated

18.2 To What extent Would a Large Scale Biofuel Production Really Replace Fossil Fuels?

18.2.1 Biomass and Biofuels

The terms biomass and biofuels are most often used as synonyms, as if liquid portation fuels were the only way to extract energy out of photosynthetic substrates

trans-1 It is to be noted that the European energy strategy places special emphasis on biofuels and cates a specific target only for them For the other renewable sources it limits itself to indicating an overall share of 20% on the total energy use.

indi-2 EUROSTAT data-base.

“Biomass” indicates all kinds of organic materials (mainly compounds of carbon,nitrogen, hydrogen and oxygen) derived from photosynthesis, including the wholemetabolic chain through animals and human societies, yielding animal products andall kinds of waste materials from the use and processing of organic matter use.While it is not always true that the main value of biomass relies in its actual energycontent, it cannot be disregarded that biomass can be converted to energy via severalconversion patterns, including processing to biofuels (Fig 18.1).

“Biofuels” in general indicates liquid products from biomass processing, to beused for transportation purposes The same term sometimes also refers to gaseouscompounds (biogas) It clearly appears that biomass (including waste materials) isthe substrate generated via photosynthetic or metabolic processes, while biofuel isonly one of the possible products of biomass processing (together with heat, biogas,electricity, chemicals) Misunderstanding the difference between biomass and bio-fuels leads to erroneous estimates about the potential of energy biomass in support

to human activities Processing biomass into biofuels requires specifically-grownsubstrates and several conversion steps, each one characterized by its own efficiencyand conversion losses Instead, direct biomass conversion to heat or waste biomassconversion to biogas is most often characterized by better performance, and is there-fore more likely to provide a contribution to at least a small fraction of the energyrequirement in sectors other than transportation systems A correct understanding ofthe role of biomass would help meeting the EU requirements for increased share ofbiomass energy, without competing with food production (cropping for energy) andwilderness conservation (energy forest plantations) In the following of the present

Fig 18.1 Biomass to energy conversion patterns.

Source: Turkenburg et al., 2000

paper, however, we will limit our focus to biofuels from sugar, cellulose and seed-oilsubstrates, in order to check their availability, feasibility, and desirability.

18.2.2 An Overview of Results

The systems considered in the following data set are: (i) corn-bioethanol;(ii) sunflower-biodiesel; and (iii) fast-growing wood production for methanol Theproductivity of biomass is based on average values found for the Italian agriculture.Conversion of these substrates to biofuel was estimated using data from commer-cially available technologies from literature

To ensure that all significant input and output flows have been accounted for, apreliminary mass balance was performed, at the local and global scales The localscale is the spatial scale within which the process actually occurs Inputs accountedfor at this scale are those that actually cross the local system boundaries The globalscale is the scale of the larger region (or the biosphere as well) within which all theprocesses that supply inputs to the ethanol system occur For instance, the electricityinput has no associated mass or emissions at the local scale, but the mass of fuel oilburnt and chemicals released for electricity production are accounted for on theglobal scale The fuel oil input on the local scale requires an additional crude oilinvestment (and related emissions) on the global scale, for extraction, processingand transport Local scale evaluation offers useful information about the investi-gated process and possible technological improvements Global scale evaluationoffers a better picture of the relationship between the investigated process and theenvironment (when considered both as a source and a sink), in order to understandsustainability

Mass evaluation on the global scale was performed according to the MassFlow Accounting method (Schmidt-Bleek, 1993; Fischer-Kowalski 1998; Bargigli

et al., 2004) It provides indicators of the indirect demand for abiotic and bioticmaterial input as well as water (the so-called material intensities) and quantify thecontribution of the process to the withdrawal and depletion of material resources

on the large scale The amount of matter that is processed and diverted from itsnatural pattern was also assumed as a measure of potential environmental distur-bance by some authors (Hinterberger and Stiller, 1998) A similar procedure for thecalculation of direct and indirect energy flows has also been performed (Embod-ied Energy Analysis, Herendeen, 1998; 2004) in order to assess the energy cost ofone unit of output (either substrate or biofuel) and the overall efficiency of biofuelproduction processes From the embodied energy data and fuel used directly wealso calculated the local- and global-scale airborne emissions Finally, the EmergySynthesis method (Odum, 1996; Brown and Ulgiati, 2004) was used to assess theecological metabolism of each investigated pattern, based on the quantification ofthe environmental support needed for the process to occur

Table 18.1a lists the main input flows to typical corn and sunflower productions

in Italy, while the main input flows to industrial bioethanol and biodiesel productionprocesses are shown in Table 18.1b Table 18.2 compares the mass- and energy-based

Table 18.1a Input flows to corn and sunflower production (average estimates per hectare per year,

local scale, Italy 2004) – Section 18.2.2

Loss of topsoil (due to erosion) t/ha/yr 20.0 17.2

Phosphate fertilizer (P2O5) kg/ha/yr 82.0 86.0

Insecticides, pesticides and herbicides kg/ha/yr 5.4 4.3

Electricity for irrigation pumps GJ/ha/yr 2.0 //

Steel for agricultural machinery (annual share) kg/ha/yr 13.6 5.2

Annual services (cost of input flows) $/ha/yr 890.0 292.9

Additional input flows due to the harvest of 70% of residues (increased soil erosion and water use are not accounted for)

Machinery for residues (annual share) kg/ha/yr 2.6 0.6

Main output flows

Residues in field as such, dry matter t/ha/yr 4.6 2.6

indicators calculated for bioethanol, biodiesel and biomethanol, under the followingassumptions:

a Use of 70% of residues as process energy source (the remaining 30% being left

in field) and credit to DDGS and seed oil cakes equal to their replacement value,i.e the energy value of the substitute product replaced in animal nutrition

b Use of 70% of residues as process energy source (the remaining 30% being left

in field), but with no energy credit for animal feed replacement

c No residues as process energy source, but energy credit for animal feed ment

replace-d No residues as process energy source and no energy credit for animal feed placement

re-Overall indicators of material demand may appear larger than expected This is anoutcome of the adopted large-scale approach For example, 1 g of processed ironrequires about 4 to 5 g of iron ore plus other biotic and abiotic materials (includ-ing large amounts of water) that are directly and indirectly involved in the process

Table 18.1b Input flows to industrial bioethanol and biodiesel production (average estimates per

hectare per year, local scale, Italy 2004)–Section 18.2.2

Residues in field as such, dry matter t/ha/yr 4.6 2.6

Steel for transp machinery (annual share) kg/ha/yr 2.4 0.3

Diesel for transport of seeds to plant kg/ha/yr 3.0 0.9

Steel for plant machinery (annual share) kg/ha/yr 44.1 4.1

Cement in plant construction (annual share) kg/ha/yr 78.4 35.2

Energy for hot water/steam generation (ass- GJ/ha/yr 0.1 2.3

uming partial use of agricultural residues)

Methanol for blending with seed oil kg/ha/yr // 87.1

Labor for plant construction and operation hrs/ha/yr 3.2 0.8

Annual capital cost and services $/ha/yr 222.4 238.6

Main output flows

The same holds for electricity, fuels, and fertilizers Furthermore, since the mass ofbiofuels is always much lower than the mass relative to the processed substrate, thelarge scale assessment increases the value of all indicators per unit of net product, asclearly shown in Table 18.2 Water appears to be the dominant (and maybe limiting)factor, as will be discussed later on, although abiotic inputs as well as disaggregateddata about fertilizers and pesticides are also sources of concern

The overall energy advantage, on a purely thermodynamic level, is indicated bythe output/input energy ratio, also expressed in Table 18.2 as a crude oil equivalentcost per unit of output First of all, the increase of the unit energy cost (in terms ofoil equivalent per gram of product) from the production of substrate to the produc-tion of the fuel is remarkable for all the crops considered This indicates an energybottleneck (and a significant energy loss) in the conversion step from substrate tofuel Producing the substrate provides a concentration of net (photosynthetic) en-ergy, while converting it to biofuel erodes most of the initial energy availability.The energy “gain” of agricultural substrate production ranges approximately from

2 to 4 (Table 18.2), whereas it drops down to about 1 (and less) after the conversion

to biofuel Finally, the best net-to-gross ratio is obtained by: ethanol in the option(a); methanol in option (b); and biodiesel in option (c) Anyway, all these valuesare in the range 1.1–1.5, which is not enough to ensure a self-sufficient production

Table 18.2 Global matter and energy flows and ratios in selected substrate and biofuel production

in Italy (average values, 2004) – Section 18.2.2

Substrate production (wet matter) Corn Sunflower Wood Oil equivalent demand per unit of substrate g/g 0.09 0.24 0.05 Fertilizers and pesticides demand per unit of

substrate

Material intensity, abiotic factor g/g 1.73 5.33 n.a Material intensity, biotic factor g/g 0.09 0.31 n.a Material intensity, water factor g/g 1238.20 1128.74 n.a.

Labor and services demand per unit of

substrate

hrs/kg 0.003 0.015 0.002 Land demand per unit of substrate m 2 /kg 1.32 4.55 0.003 Economic cost per unit of substrate $/kg 0.16 0.13 n.a.

Biofuel production Ethanol Biodiesel Methanol

Oil equivalent demand per unit of

Labor demand per unit of biofuel hrs/kg 0.02 0.04 0.01 Land demand per unit of biofuel m 2 /kg 5.10 11.48 12.6

Net energy return per hour of applied labor MJ/hr 613.55 145.77 133.08 Economic cost per unit of biofuel $/kg 0.50 0.61 n.a.

Waste and releases

CO 2 released per unit of substrate g/g 0.32 0.98 0.38

CO 2 released per unit of biofuel g/g 2.02 3.21 1.54 Industrial wastewater released per unit of

biofuel

Energy output/(direct and indirect) energy

input for substrate

Energy output/(direct and indirect) energy

input for biofuel

Ethanol Biodiesel Methanol

(a) Use of residues as

energy source, credit for

Net-to-gross energy ratio 0.13 <0 0.09

(c) No residues as energy source, credit for

of biofuel, due to the feedback loop discussed above Much to our surprise, thebiodiesel option performs even worse than the bioethanol option, in spite of theoften claimed performance of oilseed crops.

18.2.3 The Energy Return on Investment (EROI)

For an energy process to be feasible, the energy it provides must be higher thanthe energy it requires When the energy cost of recovering a barrel of oil becomesgreater than the energy content of the oil extracted, production will be discontin-ued, no matter what the monetary price may be This requires the definition of the

“energy cost” of energy, and the introduction of the so-called EROI (Energy Return

on Investment, Cleveland et al., 1984; Cleveland, 2005) (Fig 18.2)

In short, the EROI is defined as the ratio of the energy that is obtained as output of

a given energy extraction process to the total energy that is invested for its extraction,processing, and delivery, including the energy embodied in the goods and machin-ery used The lower the EROI, the smaller the net advantage provided by a givenenergy source Investing one joule in a source with high EROI, provides a net return

of many joules in support of the investor’s economy Fossil sources provided highEROI’s in the past, up to 100:1, but values have been declining down to the present20:1, as shown by Cleveland (2005), due to the exploitation of the most favourableand higher quality fossil reservoirs, and are expected to decrease further Figure 18.2also defines the net energy of a source and shows the relation of EROI to the net-to-gross ratio, the latter being the fraction that the net energy is of the total energydelivered by a process to the investor A net-to-gross ratio lower than one means that

a source does not deliver any net energy Such a ratio can be used as a measure of theability of a source (or a fuel) to support societal activities Society needs energy torun economic (agriculture, industry) and service (transportation, education, healthsectors, etc) activities A high EROI allows society to run more activities out of

a small investment in the energy sector When EROIs of energy sources decline,the same gross energy expenditure translates into a smaller net, after subtractingconversion losses and energy investment Figure 18.3 describes four scenarios ofdifferent EROI values The higher EROI (20:1) characterizes the present situation

of fossil fuels, the lower (1.2:1) characterizes the present situation of most biofuels

Fig 18.2 Definition of

EROI – Energy Return on

Investment

n i c r t x e y r e n E

g i s e o r p d a y

r e n E e r u s

Ein

Eut

E

= y r e n E e

N ut– EinE

= I O R

E ut/ Ein

E (

= o i a R s o r G - o t - t e

N ut– Ein) Ein= – 1 / E R O I

Fig 18.3 Comparison of the energy investment needed and net energy available for Italy 2004

Note: total energy expenditure of Italy 2004 (200 Mtoe/yr) dealt with according to the assumed use

of four energy sources with different EROIs (Energy Return on Investment) The higher EROI (20:1) characterizes the present situation of fossil fuels, the lower (1.2:1) characterizes the present situation of most biofuels

It clearly appears that the net energy available to a society running on biofuelswould be much smaller (23 Mtoe/yr out of 200 Mtoe/yr of gross energy expendi-ture) and therefore not much would be left to support development and growth Ofcourse, it is possible to decrease conversion losses, use resources more effectively,increase recycling patterns, decrease luxury consumption, reverse population trends,and still keep a life style at an acceptable level (Odum and Odum, 2001; 2006) evenrunning on lower EROI sources However, Fig 18.3 together with a careful look

at the breakdown of societal energy consumption in the different sectors (healthand education, primary production, transportation) indicates that EROI values lowerthan 4:1 are unlikely to support a developed society Such a threshold value for theEROI is typical of average renewable energies (solar and wind), but is not typical ofthe present biofuel sector

18.2.3.1 EROI and Biofuels

A biofuel option should therefore provide more energy than is invested, to beenergetically and economically viable, i.e should have a high EROI and a highnet-to-gross ratio This is almost never the case with the processes investigated inthis chapter For example, the output/input energy ratio of bioethanol productionfrom corn is 0.58, with no positive return in terms of net-to-gross ratio (option d,Table 18.2) If so, there is no reason for investing in the form of crude oil moreenergy than is recovered in the form of ethanol Improvement of the global effi-ciency of the process may come from a better use of agricultural and distillation

Energy

investment Conversion

losses Net

energy

by-products Higher EROIs are calculated for alternatives where DDGS and residuesare used (respectively 0.65 and 1.15 in Table 18.2) However, only when the twoby-product use options, residues and DDGS, are used together as in alternative(a), we get a significant improvement of the EROI up to a value of 1.50 Similarconsiderations apply to biodiesel, for which the best performing option is option(c), with no residues as energy source, credit for feedstock use, yielding an EROIequal to 1.51 A very low EROI equal to 1.10 is shown by methanol from wood,also by using all available residues as process heat.

Comparison with previous studies confirms our results by providing even worseperformances CCPCS (1991) reported an output/input energy ratio of 1.02 forethanol from corn in France (country average), without residue use Marland andTurhollow (1991) calculate an EROI = 1.13 for average USA Their figure increases

up to about 1.27 when an energy credit is assigned for use of coproducts Shapouri

et al (1995) calculated a value of 1.01 as an average of nine states in the U.S.,without any use of co-products When these Authors assigned an energy credit forDDGS, their average energy ratio increased to 1.24 For comparison, it is worth not-ing that Giampietro et al (1997) calculate EROIs in the range 2.5–3.5 (net-to-grossratio= 0.6/0.7) for Brazilian sugarcane, with bagasse used to supply process heat.This last result is likely to be among the best performances for ethanol productionfrom any crops that have been published

For a more complete and more up-to-date comparison, it is worth mentioning astudy about the production of soybean in Brazil and export to Europe for fuel andfeedstock purpose, as a consequences of the recent European directives in matter ofbiofuels (Cavalet, 2007; Cavalet and Ortega, 2007) The Authors calculated firstly anEROI of 2.30 by allocating a large amount of input energy to soy cakes to be used asanimal feedstock, and then a more realistic 1.23 without such an allocation In fact,when a large production of biofuels is performed in order to meet the required re-placement of fossil fuels, the related production of animal feedstock largely exceedsthe demand of the livestock sector, so the produced DDGS and oilseed cakes arerather to be considered a waste to be disposed of than an additional useful product

It is worth noting that there is still large uncertainty about data, conversion cients and results with bioenergy production worldwide Hoogwijk et al (2003) andBerndes et al (2003) evaluated the results of 17 earlier studies on the subject and ex-trapolated a final evaluation of biomass potential up to the year 2050 These authors,who are not in principle negative to bioenergy use, point out that “the main conclu-sion of the study is that the range of the global potential of primary biomass (inabout 50 years) is very broad quantifed at 33-1135 EJy−1.” (Hoogwijk et al., 2003).Such a large range indicates how uncertain a biomass based development is Thesame authors identify the reasons for the uncertainty by underlining that “crucialfactors determining biomass availability for energy are: (1) the future demand forfood, determined by population growth and diet; (2) the type of food productionsystems that can be adopted world-wide over the next 50 years; (3) productivity

coeffi-of forest and energy crops; (4) the (increased) use coeffi-of bio-materials; (5) availability

of degraded land; (6) competing land use types, e.g surplus agricultural land usedfor reforestation It is therefore not “a given” that biomass for energy can become

available at a large-scale ” (Hoogwijk et al., 2003) and conclude that “the questionhow an expanding bioenergy sector would interact with other land uses, such as foodproduction, biodiversity, soil and nature conservation, and carbon sequestration hasbeen insufficiently analyzed in the studies It is therefore difficult to establish towhat extent bioenergy is an attractive option for climate change mitigation in theenergy sector” (Berndes et al 2003).

18.2.4 The Claim for Renewability

Table 18.3, based on the approach of eMergy synthesis (Odum, 1996; Brown andUlgiati, 2004), looks at biofuels from another point of view, their global renewabil-ity EMergy measures the direct and indirect environmental support to the processgenerating a given output That is, it assesses solar and solar-equivalent flows ofavailable energy invested over the whole chain of transformations leading to thefinal product The eMergy intensity of a product (so-called transformity, or spe-cific eMergy) is therefore a measure of the ecological renewability of that product,i.e how much it takes in terms of embodied time and space to make the product

Table 18.3 Solar transformities of selected fuels and biofuels (figures also include the eMergy

associated to labor and services) – Section 18.2.4

Refined fuels (petrol, diesel, etc) 1.11E+05 (Odum et al., 2000) Hydrogen from water electrolysis (◦ 1.39E+05 (Brown and Ulgiati, 2004) Hydrogen from steam reforming of natural gas 1.93E+05 (after Raugei et al, 2005) Hydrogen from water electrolysis (*) 4.04E+05 (Brown and Ulgiati, 2004)

Ethanol from sugarcane 1.86E+05–3.15E+05 Ulgiati, 1997

Electricity from renewables (§) 1.10E+05–1.12E+05 (Brown and Ulgiati, 2004) Electricity from fuel cells natural gas powered 2.18E+05–2.68E+05 (after Raugei et al, 2005) Electricity from thermal plants (#) 3.35E+05–3.54E+05 (Brown and Ulgiati, 2004) ( ) using wind- and hydro-electricity

(§) wind and hydro

(*) Using coal and oil powered thermoelectricity

(#) coal and oil powered thermal plants

Note: Transformities have been recently revised, based on a recalculation of energy contributions done in the year 2000 by Odum et al (2000) Prior to 2000, the total emergy contribution to the geobiosphere that was used in calculating emergy intensities was 9.44 × 10 24 seJ/yr Adopting a higher global emergy reference base – 15.83 ×10 24 seJ/yr – changes all the emergy intensities which directly and indirectly were derived from it This explains a slight difference with values previously published.

available A careful look at Table 18.3 shows that the transformities calculated forbiofuels are never lower than those for fossil fuels Biofuel transformity values are

in the same range as electricity and hydrogen from fossil fuel powered plants Thissimply indicates that, since biofuels are produced via multi-step processes all char-acterized by conversion losses and supported by non-negligible amounts of fossilfuels, they share the same non-renewable characteristics as other fossil fuel poweredprocesses Actually according to this index they are even performing worse thanfossil fuels themselves

18.3 Physical Constraints Other than Energy

18.3.1 Land and Water Constraints

The available amount of arable land and water are usually neglected in most yses To feed people adequately about 0.5 ha of arable land per capita is needed(Lal, 1989), yet only 0.27 ha per capita worldwide (WRI, 1994) and 0.25 ha percapita in Italy are available (ISTAT, 2007) The world population increase andthe parallel increase of land erosion and degradation are not likely to help solvefood shortages and malnutrition Intensive agriculture is undoubtedly increasingsoil erosion worldwide (Pimentel et al., 1995) Crop yields on severely erodedsoil are lower than those on protected soils because erosion reduces soil fertil-ity and water availability, infiltration rates, water-holding capacity, nutrients, or-ganic matter, soil biota, and soil depth (OTA, 1982, 1993; El-Swaify et al., 1985;Troeh et al., 1991) Cropping for energy will compete with arable land use forfood production Available arable land is already a scarce resource Worldwide,only Canada, USA, Argentina and France are able to export significant amounts ofcereals (Giampietro et al., 1997) Wackernagel and Rees (1996), after introducingtheir “ecological footprint” concept, calculated that only Canada and Australia havefootprints that exceed their endowment of ecologically productive land Croppingmarginal or set aside lands for fuel would negatively affect wildlife (one of the mainreasons set aside policies have been introduced) and would provide lower yieldsdue to lower productivity of marginal lands and higher energy demand for culturalpractices However, even if competition with food were not taken into account, inthe hope that better yields or genetic improvements could help solve this problem,the need of high biomass yields for efficient biofuels production would cause anadditional pressure on land and accelerate the process of soil erosion and depletion.Topsoil formation by natural processes is a very slow process, and organic matter insoil should be considered a nonrenewable resource

anal-Table 18.2 shows that 5.1 m2of land are needed in Italy to yield 1 kg of ethanoland 11.5 m2per kg of biodiesel Total energy use in the transport sector in Italy isabout 44.4 million tons of oil equivalent per year (ISTAT, 2007), i.e about 31% ofthe overall energy use in the country How much land is actually available in Italyfor biofuel production? A careful look at Table 18.4 offers a clear picture of the