Features

�DISCUSSION

DISCUSSION New Biotechnology � Volume 25, Number 1 � June 2008

Features

Biofuels are dead: long live biofuels(?) –Part one

Andrew Moore, andrew.moore@embo.org

Beleaguered by criticisms, and abused by politicians for ecological

target-setting, biofuels are in their darkest hour. But their bringing

to trial should remind us – yet again – of something else: the highly

questionable sustainability of most of modern agriculture. Is this the

end of biofuels? Probably not, but it is certainly the end of a cheap

solution to the problem of sustainable portable fuels. Part one of this

two-part article focuses on the political and agricultural dimensions

of the topic.

Targets, politics and propaganda

‘‘. . .most first generation biofuels have a

detrimental impact on the environment. . . The

[UK] government and EU’s neglect of biomass

and other more effective policies to reduce

emissions in favour of biofuels is misguided.’’ Our

point of departure for this journey through

policy, science and technology is two reports

from the United Kingdom. The starting quote is

from the concise and hard-hitting report by the

UK parliament [1] released in January this year, a

week after the Royal Society had brought out its

90 page policy document on biofuels [2].

Summarising expert wisdom, presenting

extensive information and data, the Royal

Society report reaches similar conclusions, but in

a more reserved style: first-generation biofuels –

that is, mainly thosemade from grain, corn or oil-

seed (Table 1 and Figs 1 and 2) – are generally

unsustainable, and more attention needs to be

given to second-generation biofuel

development – which uses whole plant matter.

Hot on the heels of both reports was a proposal

6 www.elsevier.com/locate/nbt

from the European Commission for a new

renewable energy directive [3]. How timely.

What a pity the Commission had not been

able to read the UK reports. As the Royal Society

report emphasises, governments have so far

placed too much emphasis merely on setting

targets for percentage substitution of fossil fuels

by biofuels, without proper regard to their true

sustainability. The UK parliament report

recommends nothing short of a moratorium on

biofuels. Angered and confounded by this

observation, Brussels could do no more than

restate the urgency of rapid action to counter

global warming. Perhaps that is because the

Commission had set its heart on another target:

that of becoming the world leader in combating

climate change. The Commission’s proposal for a

new renewable energy directive still mentions

the substitution target for transport fuel set in

2003, that is 10% by 2020. But something is

going horribly wrong: the goal of 5.75% by 2010

is not even being reached with unsustainable

methods. A progress report from the

1871-6784/$ - see front matter � 2008 Els

Commission itself contains predictions of

between 2.4% and 4.2% substitution by 2010 [4].

Worse still, a higher target looms for 2020, and

must be achieved via sustainable production

that does not even exist.

As Gail Taylor, Professor for Plants &

Environment, University of Southampton, UK,

pointed out ‘we won’t [reach those targets] from

European-grown crops. We don’t have the

framework in place to ensure sustainability.

Setting that 5.75% target had a very detrimental

effect because it drove our markets towards

using existing crops in an unsustainable way.

We’ve got to do quite a lot of work pretty quickly

to get these things right.’ Essentially a bad trend

has to be reversed, and production has to be

increased at the same time. EuropaBio (the

European biotech umbrella organization) alludes

to this quandary in its response to the

Commission’s proposal [5]: ‘‘As an important

measure in order to stimulate the transition

towards (next generation) biofuels with higher

greenhouse gas savings, EuropaBio proposes a

‘step-wise approach’ starting with a relatively low

greenhouse gas savings threshold. . .’ Of course,

otherwise many producers would go out of

business between now and 2020. But is it

inevitable that we will have to live with the ‘bad’

biofuels for some time to come?

The way out of this apparent dilemma is also

to be found in the Royal Society report: more

research and analysis (ranging from land use to

sociology). Truly sustainable biofuels will not

come cheap, because the real cost should

include the extra research and development

needed to create and bring them to consumers.

There does not seem to be a way out of that

corner: whether via financial incentives from

governments to R&D industry, or via public

money flowing directly into academic R&D, the

tax-payer or consumer will have to foot the bill.

evier B.V. All rights reserved. doi:10.1016/j.nbt.2008.04.001

New Biotechnology �Volume 25, Number 1 � June 2008 DISCUSSION

TABLE 1

Comparison of commercial first and second-generation biofuels at current technological status

First generation Second generation

Produced only from the primary crop (e.g. grain, sugar, or oil-seedcomponent of the plant); the rest of the plant is not used for fuel

Produced from whole plant matter, or ‘waste’ matter left after

harvest of primary crop, forestry waste or wood processing waste

Substance converted into fuel: Starch, sugar and oil Substance converted into fuel: mainly lignocellulose

Examples: corn, wheat, sugar cane and sugar beet, rapeseed,palm fruit, soy beans etc. = mostly annuals

Examples of purpose-grown crops: switchgrass, miscanthus,

coppice willow, alfalfa etc., mixed crops = perennials

Carbohydrate contents of grains, and sugars (cane and beet),are easily fermented to ethanol with low technology apparatus

Entire plant material is converted into fuel. Main methods, either

Oils are processed into automotive grade fuel 1. Fermentation, producing ethanol and methane,

leaving solid waste for pelleting and burning (e.g.)

in heat-and-power stations: relatively cheapBoth methods are of relatively low monetary cost 2. High-temperature/high pressure decomposition and

catalytic synthesis processes: relatively expensive

Crops are grown on existing agricultural land by existing farmers.This land is easily defined and worked: yields are predictable

Crops can (theoretically) be grown on less valuable land that is

not suitable for food/feed agriculture. But it is uncertain thatsignificant amounts of fuel could ultimately be made from

such ‘marginal’ and low-quality land

Crops are directly in competition with food, hence leading to price-linkage Crops are less in competition with food, but degree of

competition depends on the land used

Crops are energy-intensive: for example need large quantities of fertiliser Crops in principle need less fertiliser, and are less energy-intensive

Energy balancesa tend to be modest or even negative if crop is only grownfor fuel production, because of the high-input nature of food-crop

agriculture. Sugar cane and beet may be an exception to this rule

Energy balancesa can be substantially above 1 (possibly as

high as 60 or more), especially if little/no fertiliser is used.

Perennial plants can be left growing and part-harvested at

intervals, thus removing the need to re-plant

Prospects: generally doomed, except possibly for sugar cane and beetin certain circumstances

Prospects: could be important, especially with developments

in plant genetic engineering, systems biology and novel

low-temperature chemical catalysisa Energy balance is the per unit mass ratio of total energy released on burning the fuel to total energy inputs in producing the fuel (from plant seed production to fuel distribution).

Features�DISCUSSION

Insulating consumers from the financial costs of

sustainable biofuels will prove harder in the

short term than hiding the environmental costs

of unsustainable ones. And that is how it should

be: to achieve a sustainable world society we

should be using less of everything and

concentrating more on quality. We are trying to

replace oil and coal that took nature hundreds of

millions of years to produce with equivalents

that we produce in the laboratory in a matter of

hours. It is hard to imagine how a fast transition

(geologically speaking) to renewable

alternatives can be done cheaply.

As subsidies and other political incentives for

biofuel production tumble like dominoes across

Europe [6,7], it becomes clear that there has

been too much concentration on the supply

side. ‘Current policy frameworks and subsidies

for biofuels are not directed towards reducing

greenhouse gas (GHG) emissions, but rather

provide incentives for national supply targets’

says the Royal Society report. There is no doubt

that incentives are necessary, but these should

be linked to increased biofuel efficiency and

minimisation of environmental impact, for

example – measures that are much harder to

analyse than the mere progress toward a

production target. The Commission is right to

feel urgency, but perhaps it should direct it

elsewhere: a few unsustainable biofuels are now

cost-competitive and already in the market

place. How do we deal with the problem of

withdrawing them from circulation, especially if

their introduction was part of a political

incentive (e.g. for farmers to convert to biofuel

production)? Although EU subsidies for biofuel

production – s90 million per year – are pathetic

compared with US ones, growth in EU land use

for biofuels is impressive [8]: in 2004 farmers

applied for subsidies for a mere 310,000 ha; in

2007 it was 2.8 million ha – an area about the size

of Belgium – the vast majority of it for ‘bad’

biofuels.

As Jonathan Jones, head of the Sainsbury

Laboratory for plant research, John Innes Centre,

Norwich, UK, remarked ‘Biofuel subsidies were a

way to create a push for people to go in what

was thought to be the right direction, but with

real ignorance on the part of decision makers.’

There is a real risk that without policy support of

technologies embodying low GHG emissions,

low environmental impact and low costs, we

could be ‘locked into a system that is sub-

optimal, both in terms of efficiency and

sustainability’ according to the Royal Society.

Americans are already locked into a feeding the

first-generation biofuel cuckoo in their nest to

the tune of US$ 6 billion for bioethanol and US$

5 billion for biodiesel per year.

At least Brussels can console itself with not

being alone in setting ambitious targets without

really knowing how to get there. In the USA, the

federal government has set a target of 30%

substitution of transportation fuels with biofuels

by 2030 [9]. Though the route to this goal is

unclear, the motivation is anything but: an

increasing desire for energy security and

independence from politically difficult oil-

producing regions of the world. Environmental

concerns play a minor role. Many ordinary

people are also attracted by the dream of

independence from the petrol pump. Recipes for

do-it-yourself biodiesel manufacture [10] are

easy to find on the Internet. With a kitchen

blender, some methanol, drain-unblocking

pellets and used cooking oil you’re already

halfway there. Chemical burns and intoxication

are probably the least of our worries if it takes

off in a big way. Doubtless, nobody has

attempted a full life-cycle assessment of this

technology.

www.elsevier.com/locate/nbt 7

DISCUSSION New Biotechnology � Volume 25, Number 1 � June 2008

FIGURE 1

Examples of first-generation biofuel crops. (a) Corn (source: Texas A&M University, Department of Soil & Crop Sciences, USA), (b) wheat (source: Kansas StateUniversity, USA), (c) oil-seed rape (source: US Fish and Wildlife Service) and (d) tropical oil palm (source: http://www.plantsystematics.org/).

Features

�DISCUSSION

Even if the wanton target-setting is removed,

the biofuel movement might better be viewed

as an attempted solution to a political and socio-

economic problem rather than to the

environmental one. Political interests (especially

economic competitiveness), intransigence,

FIGURE 2

Examples of second-generation biofuel feedstocks. (a)Energy Crop. (http://www.switchgrass.nl/)), (b) miscanwillow (source: University of Nottingham, UK) and (d)(http://www.arkansasrenewableenergy.org/) and (e) w

8 www.elsevier.com/locate/nbt

convenience and ingrained habits all tie us

strongly to hydrocarbon portable fuels.

Predictions indicate that by 2020 the

largest increases in GHG emission will arise

from the transport sector [4]; electricity

and the energy industry – though a larger

Switchgrass (source: Switchgrass as an Alternative

thus (source: University of Illinois, USA), (c) coppicecorn stover (source: Arkansas Renewable Energy

ood chippings (source: ec.europa.eu).

fraction of total fossil fuel use – are predicted to

diminish their GHG emissions in the same

period (Fig. 3). Global warming or not, nobody

can be sure how much longer we can

economically mine oil. However, reductions

in our use of fossil fuels are unlikely to

come faster than the rate at which we research

and develop alternatives. At the very least,

second-generation biofuels should be

accompanied by an attempt at second-

generation political thinking. As to whether

biofuels can truly be sustainable? We might

have to wait a while. And while we wait, what

better to do than perform full-cost life-cycle

analyses.

Of cans of worms and other hidden

nasties. . .

What has gone wrong with the sums? It is a bit

like the sub-prime mortgage problem and the

instability in the financial markets at present. The

economy was thriving (we were told), share

prices were booming, but some parts of the

equation were missing: What really underpins all

the borrowedmoney used to drive the economy,

and how did I manage to pay so little for that CD

player I just bought? That many, if not most,

biofuels today tend to take from one place in an

unsustainable way to give in another sector –

apparent reduction in net CO2 emissions per unit

mass burnt – is widely recognised. What is

commonly missing is a proper analysis of every

part of the process between land use and origin

New Biotechnology �Volume 25, Number 1 � June 2008 DISCUSSION

FIGURE 3

Predicted changes in CO2 emissions by sector for the period 2005–2020. Source: PRIMES model (http://www.e3mlab.ntua.gr/ or http://www.e3mlab.ntua.gr/downloads.php), as published in the European Commission’s Biofuels Progress Report, 10 January 2007.

Features�DISCUSSION

of the plant material through to combustion of

the biofuel: ‘hidden’ costs to the environment,

such as transport of the materials, often remain

just that: hidden.

But it is ‘fiendlishly complex’ as Jonathan

Jones notes. If – after assessing various research

papers, reviews and policy documents on the

subject – a dispassionate observer were not

completely confused, he would most probably

be under-informed. Analyses generally fall into

two categories: (1) boundary-setting and (2) life-

cycle (the consideration of as many as possible

identifiable energy costs involved up to the point

of combustion of the fuel).

Any review of biofuels would be incomplete

without a contribution from one of its starkest

opponents, David Pimentel, a professor at

Cornell University, USA. ‘I do have a positive

statement to make about biofuels: we burn

waste wood in the USA. And the thermal energy

provides 3% of our domestic energy

consumption’, he said. But that is where is

optimism ends. An entomologist by background,

Pimentel has increasingly engaged with the

biofuel debate, and over 25 years written books

and co-authored articles about the relationships

between food, fuel, the economy and

population. He is most known for his criticisms of

first-generation bioethanol production. His life-

cycle analyses – suggesting disastrous energy

balances for bioethanol and biodiesel

production – are criticised by his opponents for

the use of old data. However, his much simpler

boundary-setting calculations seem rather

persuasive. ‘The energy contained in all the

vegetation across the whole USA only accounts

for around 1/3 of the total energy consumed in

the USA per year’ he told me.

How is this calculation done? The figure for

total primary energy consumption in the USA is

given by the DOE as around 100 � 1015 BTU [11]

(see definitions and conversions). Pimentel’s

research colleagues have collected data (as yet

unpublished) suggesting that the total plant

biomass (farmland, plus all forests, grasslands

and other non-agricultural land) in the USA

contains a mere 32 � 1015 BTU of energy. The

transport uses of fossil fuels in the USA alone

amount to 29 � 1015 BTU. This certainly makes

biofuels look like a lost cause, even at amoderate

percentage substitution, because the calculation

takes no account whatever of energy inputs in

‘theoretically’ turning all of America’s plants into

fuel.

Anyone with a computer and Internet

connection can find the data to do a similar

calculation, and so I did.

I found the total area of cultivatable farmland

in the USA (so-called ‘total acres operated’) from

the USDA website [12]:

900; 883; 000 acres ¼ 364; 587; 350 ha

Figures for total above-soil plant matter

production per year of between 12 and 18 dry

tons/ha for commercial maize varieties are

common in the literature [13–15], so I chose a

seemingly conservative value of 12 tons/ha.

That gives

12 � 103 kg � 364,587,350 ha = 4.4 � 1012 kg

dry biomass.

The specific calorific value of corn stover – the

material discarded after harvest – is consistently

quoted at around 17,000 BTU/kg (dry mass)

[16,17], and the value for the whole plant,

including corn, cannot be much different (if

anything it is higher). David Pimentel told me

that he had used a very similar value for his

boundary-setting calculation.

So, 4.4 � 1012 kg � 17,000 BTU/kg =

7.4 � 1016 or 74 � 1015 BTU.

For comparison, remember, the total transport

fossil fuel use is 29 � 1015 BTU/year.

Here was my first boundary, which –

incidentally – looked more positive than

Pimentel’s calculation. I congratulated myself on

such good work. Unrealistic though it was, I had

arrived at more than twice the annual calorific

value of fuel used in transport – at least, that is

the energy that the plants had sequestered. For

that, I had used the entire farm area of the USA

for growing maize.

If we assume that the farm area given above

really can be used to grow crops of the quality of

corn, then perhaps we could use 10% of that

land to make a second-generation biofuel that

uses the entire plant matter. Incidentally, a yield

of 12 tons year�1 ha�1 is also typical of certain

energy crops, such as coppice willow [18,19].

That would give 7.4 � 1015 BTU of plant matter

energy.

We could then take into account the energy

costs of producing the biofuel from this plant

matter (e.g. transport, fertilisers, other farming

costs, etc.) and give it a very mediocre energy

balance (ratio of energy contained in the fuel:

www.elsevier.com/locate/nbt 9

DISCUSSION New Biotechnology � Volume 25, Number 1 � June 2008

Features

�DISCUSSION

total energy inputs needed to make it) of 2.0 –

which is within the range of values published for

first-generation bioethanols [20]. Note, we are

producing a second-generation biofuel here,

because we are using the whole plant matter.

Still, let’s be pessimistic. At steady state, and

assuming we can use the biofuel itself – instead

of fossil fuel – for generating the biofuel, we

should still get:

7:9� 1015 � 0:5 ¼ 3:9� 1015 BTU of biofuel

ð0:5 ¼ ratio of fuel burnt for fuel madeÞ

This is almost 15% of current transport fuel

use. Even if we cannot use the biofuel to make

the biofuel, its use in transport should in net

terms equally compensate for the fossil fuel used

instead.

Of course, with the energy balance of 2.0 we

have used half as much energy to make the fuel

as the fuel itself contains, so this is very

inefficient. It certainly does not seem a very good

use of agricultural land. Still, at least the

calculation methodology was right: Pete Smith,

Professor of Soils and Global Change, University

of Aberdeen, UK, kindly looked over it for me,

and commented ‘looks reasonable’.

Then, to my horror, I discovered that the FAO

(Food and Agriculture Organization of the

United Nations) database [21] gives harvested

areas for the USA that sum to just 119,000,000 ha

– a third of my previous area. Now I would only

be able to replace 5% of transport fuel. The

President would not be pleased with me, I could

sense it already. Which land area figure was

correct? I could not find any agreement on that. I

just wanted to calculate potential, so – feeling

optimistic – I chose to stick with the higher

figure. But deep down, I was troubled.

Such different values for seemingly simple

calculations are commonplace in this field. What

I had learnt is that many calculations do not so

much attempt to fit reality as bend the mind of

the reader to interpret them as reasonable. ‘I

warned you what a can of worms this all is’

replied Pete Smith. Believe it or not, some

analyses that are frequently quoted in support of

biofuel crops do not even take account of the

energy needed to harvest and process them into

fuel, but merely the extractable energy that they

contain. An example of this (as quoted in the

Royal Society Report) is a paper showing

percentages of UK arable land necessary to

supply 5% of transport fuel from different crops

[22].

Things do not get any better with full life-cycle

calculations – the second type of analysis.

Figures for the energy balance for the conversion

to fuel of agricultural waste, for instance, range

10 www.elsevier.com/locate/nbt

from 0.8 up to 60. This is because the calculation

is greatly influenced by how we view this ‘waste’.

‘In the USA, there is a total processing capacity.

They turn maize into more things than you can

imagine. It’s almost a matter of spin as to what

you prefer to call the by-product’ noted

Jonathan Jones. If the waste is a ‘free’ by-product

of wheat production, say, then it may have a

value of 50 or more [20] (i.e. produce 50 times as

much energy as fuel compared with the energy

needed to create it and convert it to fuel). If, on

the contrary, it is regarded as part of the crop,

then the value probably lies somewhere

between 0.8 (unfavourable) and 2.4. The latter

view seems more reasonable, because if we

‘need’ this ‘waste’ then it needs to be factored

into the sustainability of agriculture as a whole.

Also it will compete with other possible uses to

which it could be put (e.g. simply burning it in

combined heat and power (CHP) stations).

It is very easy to leave out important parts of

the analysis (either by design or by mistake).

People making policy decision will not spot such

errors. But it is also genuinely very hard to

identify all energy costs that need to be

incorporated and obtain true values for them.

Should the ‘costs’ of farm employees be included

in biofuel crop production analyses? Some say

yes, but such costs are not generally included in

calculating energy balances of fossil fuels, hence

making such a comparison impossible.

It is inevitable that biofuel analyses are bolted

together from figures from diverse sources, each

representing a specialised understanding of the

particular topic (e.g. soil sciences, physical

chemistry, agricultural sciences, etc.). It is not

inevitable that we have to believe them: some

are highly hypothetical, whilst others are based

on genuine practice and attempt to reflect true

costs. First-generation biofuels have generally

been developed with an unintentional

‘externalising’ of the true costs because parts of

the life-cycle analysis were missing. But this

‘worked’ so well and so easily that producers and

politicians were loathe to look deeper into the

analysis. I paid so little for my CD player because

the people whomade it were badly paid and had

no social security – practices that, on a large

scale, ultimately damage society and are

unsustainable. First-generation biofuels are very

easy to bolt on to conventional agriculture, but

generally they do not give proper consideration

to the larger picture of agricultural or

environmental sustainability.

Avoiding treading on the giant’s sore toes

Published on 7 February this year, a paper in

Sciencexpress [23] shows just how bad some

biofuels can be when grown in the wrong places.

It’s not a new concern by any means, but the

latest figures are astounding. Ordinarily ‘bad’

biofuels – made via first-generation methods

from existing agricultural produce and land in

industrialised nations – pale into insignificance

when compared with schemes to clear non-

agricultural land for biofuel crop production. It is

estimated that clearing forest, grasslands and

other non-agricultural land to grow food-based

biofuel crops releases between 17 and 420 times

more CO2 than the annual GHG reductions that

the biofuels provide in substituting fossil fuels

[23]. That is precisely what is happening in parts

of Brazil, Southeast Asia and even the USA.

The question of where and how to grow

biofuel crops sustainably is arguably the biggest

dilemma facing the field. But more than that, it

poses serious questions for the sustainability of

the whole of agriculture as we know it. ‘Most

places where you can grow crops people are

growing them. The largest recent increases in

food production come from increased yield per

hectare’ said David Powlson, Lawes Trust Senior

Fellow, Department of Soil Science, Rothamsted

Research Institute, UK. Though crop yields

continue to rise in certain parts of the world, the

general sustainability of yields is anything but

clear, especially with the unpredictable effects of

global warming [24]. Global warming – the

stimulus for biofuel development – will probably

kill fewer people than our lack of a replacement

for the fossil fuels that drive global agriculture. In

the distant future – if other renewable energies

do not eclipse them – biofuels may be regarded

as the new oil rather than an attempt to slow

global warming. But they have to tread very

carefully.

To date, most biofuel endeavours amount to a

‘bolt-on’ addition to a fossil fuel-guzzling

agriculture, and hence suffer from most of its

faults. The difference between food and fuel is

rather one of the attitudes: when it comes to the

crunch, politicians will happily burn fossil fuel for

agriculture, because to limit global production of

food with a rising population is tantamount to a

crime against humanity. And energy-intensive

nitrate fertiliser is acceptable in food production

– but not biofuel production – because ‘There’s

no alternative for producing food, but there are

alternatives for making energy’ according to

Chris Smith. But an alternative may well have to

be found when fossil fuels become very

inaccessible and, therefore, very expensive. In

the meantime, insulated from the harsh realities

of hunger, wealthy nations that overproduce

have seen fit to place biofuels in direct

competition with food. Some form of

New Biotechnology �Volume 25, Number 1 � June 2008 DISCUSSION

FIGURE 4

Increase in world meat production, 1950–2000. Source: Data from the FAO, figure as published in Ref. [36].

Features�DISCUSSION

competition is unavoidable, as Smith pointed

out: ‘You can’t really separate biomass

production for food and fuel. The people

growing the crops are the same. One year they

grow wheat, one year they grow a biofuel crop.’

But the level of yields that allow such duel

production in the first place are possible mainly

because of fossil fuel energy.

The massive quantities of fertiliser used for

food and feed production rely on the very same

oil that we are trying to avoid using for biofuel

production. In fact, nitrate fertiliser production

(from ammonia made by the energy-intensive

Haber–Bosch process) is often the largest single

consumer of fossil fuel energy in the agricultural

process [25]. In its manufacture and use, it also

releases significant quantities of N2O, which –

per unit mass – is 300 times more potent than

CO2 [26]. In a world deprived of cheap fossil fuels,

who is to say that we could continue to produce

food on such a large scale? It is not inconceivable

that a carefully balanced obligate division of

agricultural land emerges between that used for

fuel production and that used for food and

fodder. Biofuels might even end up being more

sustainable than much of agriculture itself when

the oil dries up. But whilst oil is cheap and

biofuels have mediocre energy balances,

biofuels are seen in a completely different light.

When it comes to sustaining the fertility of soils,

biofuels will have to find more sensitive solutions

thanmassive artificial fertilisation, and – in a sense

– bemore sustainable than agriculture in general.

They must also avoid land competition with food

crops. ‘We need better exploitation of polluted

land and land that is unsuitable for food or feed

agriculture – so-called marginal land’ said David

Powlson. Tilman et al. [27] claim that biodiverse

growth on such land can give good energy

balances compared with high-input agro crops

(and estimates of GHG reductions of 6–16 times

compared with corn grain ethanol and soybean

biodiesel) that are sustainable over a ten-year

period. This work also shows that increased

species diversity leads to increased harvested

mass and quantity of carbon sequestered in the

soil, and decreased use of fertiliser and pesticide.

But whether this strategy has a sustainably low

ecological impact when practised on a large scale

is an open question: after all, even marginal land

sustains an ecosystem with particular species of

animals and plants.

If monocultures, such as switchgrass, are

grown on low quality land, the question of

fertiliser seems rather more pertinent. This

appears to be a point on which there is some

disagreement. Some claim that switchgrass is a

low-input crop. But depending on the land in

question, estimates for nitrate fertiliser of

between 112 kg [28] and 170 kg [29] per hectare

per year might be necessary just to sustain the

crop. Compared with other crops, that is not

particularly low: values of 120 (spring Barley),

150–170 (winter barley), 170–200 (winter wheat)

110–140 (potatoes) are common among

recommendations for farmers and in actual

usage [30–33]. However, where perennial

grasses are planted for the first time, and

purpose grown, they can help sequester

atmospheric carbon in the initial decades

because of their extensive perennial root

systems [27].

Sustaining the fertility of the soil is only part of

the equation. The consistency of the soil is also

important. Taking organic matter away, instead

of re-ploughing it, reduces the physical

resistance of the soil, leading to massive wind

and water-related erosion in many places (e.g.

the American Dust Bowl) [34]. This certainly

argues against a generalised use of primary crop

waste for biofuel production, though – as we will

see later – on a small scale, and in carefully

chosen places, it could work. David Powlson’s

lack of particular optimism on the subject fits

with this impression: ‘There are some niches for

perennial biomass crops, but I’m more gloomy

about plants as sources of renewable energy

than I was.’

However, it can equally be observed that we

currently use less than 1% of the entire biomass

on Earth for human purposes [35], and as Gail

Taylor commented ‘It’s hard to imagine a world

wherewe cannot increase that just a little bit.’ One

of the largest flexibilities in agriculture is our

consumption of meat. If, as a whole, the world

population could reconcile itself to eating less

meat, instead of more (Fig. 4), perhaps we could

counter hunger and grow significant quantities of

biomass. If cattle are fed grain – which is common

practice in theWest –wemust grow ten times the

amount of grain to supply a meat-eating human

with the same energy and matter as would be

needed if the person ate the grain directly [36]. Of

course, this is simply ameasure of equivalences. In

practice, it is estimated that meat-containing

humandiets require slightlymore than 25%of the

land that vegetarian diets require [37]. But even

that is a formidable area of land.

Ironically, biofuels must – if at all – be

incorporated with great sensitivity into an

agriculture that largely relies on the brute force

of massive fossil fuel energy use. If they are

bolted on to contemporary agriculture, they

simply exacerbate its problems. The best hope

for the production of biofuels might be a large

number of relatively small, well-defined

independent systems requiring short transport

distances for feed material and product. But the

science and technology behind the biofuels of

the future could make an enormous difference

to the efficiency with which their intrinsic energy

is converted to fuels. And there is no shortage of

ideas for biofuel technology to draw on.

Definitions and conversions

BTU: A British Thermal Unit (BTU) is the amount

of heat energy needed to raise the temperature

of one pound of water by one degree F. This is

the standard measurement used to state the

amount of energy that a fuel has as well as the

amount of output of any heat-generating device.

1 BTU ¼ 1; 054:8 Joules ¼ 252 Calories

References

1 UK House of Commons First Report from the Select

Committee on Environmental Audit (2008): http://

www.publications.parliament.uk/pa/cm200708/

cmselect/cmenvaud/76/7602.htm

2 Sustainable biofuels: prospects and challenges, Royal

Society (2008): http://royalsociety.org/

document.asp?tip=1&id=7366

www.elsevier.com/locate/nbt 11

DISCUSSION New Biotechnology � Volume 25, Number 1 � June 2008

Features

�DISCUSSION

3 European Commission proposal for a new

renewable energy directive (released, 23 January

2008): http://ec.europa.eu/energy/climate_actions/

doc/2008_res_directive_en.pdf

4 Biofuels Progress Report, European Commission

(2007): http://ec.europa.eu/energy/energy_policy/

doc/07_biofuels_progress_report_en.pdf

5 EuropaBio pressrelease on biofuel production targets

(2008): http://www.europabio.org/documents/

biofuels/PR_RED_biofuels_240108.pdf

6 Reuters report (October 2007) ‘‘EU trimming of

subsidies for biofuel crop production’’: http://

uk.reuters.com/article/environmentNews/

idUKL1717632220071017

7 New York Times (January 2008): http://

www.nytimes.com/2008/01/22/business/

worldbusiness/22biofuels.html

8 International Herald Tribune (October 2007): http://

www.iht.com/articles/ap/2007/10/17/business/EU-

FIN-EU-Biofuel-Subsidies.php

9 The President’s Biofuels Initiative to reduce foreign oil

dependence – summary: http://

www1.eere.energy.gov/biomass/

biofuels_initiative.html

10 Make your own biodiesel: http://journeytoforever.org/

biodiesel_make.html

11 International Energy Outlook, US Department of

Energy, figures on total consumption in various

sectors: http://www.eia.doe.gov/oiaf/aeo/

consumption.html

12 Data on total operated acres in USA: http://

www.ers.usda.gov/data/arms/app/Farm.aspx

13 Yield per hectare, corn plants, Ref. [1]: http://

www.pda.org.uk/leaflets/17/leaflet17-1.html

14 Yield per hectare, corn plants, Ref. [2]: http://

www.jar.com.pk/pdf/3-Green%20Fodder%20Yield.pdf

15 Yield per hectare, corn plants, Ref. [3]: http://

agriculture.irlgov.ie/crops_and_plants/

MZRL2006_160306.doc

12 www.elsevier.com/locate/nbt

16 Calorific value of corn stover, Ref. [1]: http://

www.omafra.gov.on.ca/english/engineer/facts/93-

023.htm

17 Calorific value of corn stover, Ref. [2]: http://

www.biofuelsb2b.com/useful_info.php?page=Typic

18 Sims, et al. (2006) Energy crops: current status and

future prospects. Global Change Biol. 12, 2054–2076

19 (2005) Assessing the potential for biomass energy to

contribute to Scotland’s renewable energy needs.

Biomass Bioenergy 29, 73–82

20 Powlson, D.S. et al. (2005) Biofuels and other

approaches for decreasing fossil fuel emissions from

agriculture. Ann. Appl. Biol. 146, 193–201

21 FAO database interface for obtaining harvested area

for all crops: http://faostat.fao.org/site/567/

DesktopDefault.aspx?PageID=567

22 Woods, J. and Bauen, A. (2003) Technology Status

Review and Carbon Abatement Potential of

Renewable Transport Fuels (RTF) in the UK. DTI;

AEAT.B/U2/00785/REP URN03/982:1-150. Available

online at http://www.dti.gov.uk/renewables/

publications/pdfs/

b200785.pdf?pubpdfdload=03%2F982

23 Joseph Fargione et al. Land Clearing and the Biofuel

Carbon Debt. Science Magazine, published online,

February 7, 2008: http://www.sciencemag.org/cgi/

rapidpdf/1152747v1.pdf

24 David B. Lobell and Christopher B. Field, Environmental

Research Letters, 2 (March 2007) 014002: http://

www.iop.org/EJ/article/1748-9326/2/1/014002/

erl7_1_014002.html

25 West, T.O. and Marland, G. (2002) A synthesis of carbon

sequestration, carbon emissions, and net carbon

flux in agriculture: comparing tillage practices

in the United States. Agric. Ecosyst. Environ.

91, 217–232

26 Global Warming Potentials (GWPs) of various gases,

according to the IPCC: http://www.grida.no/climate/

ipcc_tar/wg1/248.htm

27 Tilman, D. et al. (2006) Carbon-negative biofuels from

low-input high-diversity. Grassland Biomass Sci. 314,

1598

28 Nitrate fertiliser estimates for switchgrass, Ref. [1]:

http://www.extension.iastate.edu/Publications/

PM1866.pdf

29 Nitrate fertiliser estimates for switchgrass, Ref. [2]:

http://agron.scijournals.org/cgi/content/full/93/4/896

30 Nitrate fertiliser estimates for staple food crops, Ref.

[1]: http://www.teagasc.ie/research/reports/

environment/4568/index.htm

31 Nitrate fertiliser estimates for staple food crops, Ref.

[2]: http://agresearchforum.com/publicationsarf/

2005/03_page.pdf

32 Nitrate fertiliser estimates for staple food crops, Ref.

[3]: http://www.springerlink.com/index/

PN4259J436515170.pdf

33 Nitrate fertiliser estimates for staple food crops, Ref.

[4]: http://www.pubmedcentral.nih.gov/

articlerender.fcgi?artid=33552

34 Rattan Lal et al. (2004) Managing Soil Carbon. Science

304: 393. http://www.sciencemag.org/cgi/reprint/304/

5669/393.pdf

35 FAO Commentary piece on biomass, livestock, people

and the environment: http://www.fao.org/docrep/

W9980T/w9980T01.htm

36 Development, Productivity and Sustainability of Crop

Production: http://www.plantbiotech.jbpub.com/pdf/

chrispeels_Ch03_052-075.pdf

37 David Pimentel and Marcia Pimentel (2003)

Sustainability of meat-based and plant-based diets

and the environment. Am. J. Clin. Nutr., 78, , 660S–663S.

http://www.ajcn.org/cgi/content/full/78/3/660S

Andrew MooreEuropean Molecular Biology Organization,Science & Society Programme,Meyerhofstrasse 1, 69117 Heidelberg, Germany