Prospect has published my essay on bioenergy, in which my research left me astonished at the environmental and economic harm that is being perpetrated. Biomass and biofuels are not carbon neutral, can't displace much fossil fuel, require huge subsidies, increase hunger and directly or indirectly cause rain forest destruction. Apart from that, they're fine... Here's the text:



From a satellite, the border between Haiti and the Dominican Republic looks like the edge of a carpet. While the Dominican Republic is green with forest, Haiti is brown: 98 per cent deforested. One of the chief reasons is that Haiti depends on bioenergy. Wood-mostly in the form of charcoal-is used not just for cooking but for industry as well, providing 70 per cent of Haiti's energy. In contrast, in the Dominican Republic, the government imports oil and subsidises propane gas for cooking, which takes the pressure off forests.



Haiti's plight is a reminder there is nothing new about bioenergy. A few centuries ago, Britain got most of its energy from firewood and hay. Over the years the iron industry moved from Sussex to the Welsh borders to Cumberland and then Sweden in an increasingly desperate search for wood to fire its furnaces. Cheap coal and oil then effectively allowed the gradual reforestation of the country. Britain's forest cover-12 per cent-is three times what it was in 1919 and will soon rival the levels recorded in the Doomsday Book of 1086.



Yet if the government has its way, we will instead emulate Haiti. In 2007, Tony Blair signed up to a European Union commitment that Britain would get 20 per cent of its energy from renewable sources by 2020. Apparently neither he nor his officials noticed this target was for "energy" not "electricity." Since much energy is used for heating, which wind, solar, hydro and the like cannot supply, this effectively committed Britain to using lots of wood and crops for both heat and electricity to hit that target. David Cameron and Chris Huhne, anxious to seem the "greenest of them all," dare not weaken the target, despite its unattainability.

Biomass consumption in power stations was up 27 per cent in 2010 and "co-firing" (burning biomass alongside coal) was up 39 per cent. To replace coal, the government projects that by 2020 Britain will be generating electricity from burning up to 60m tonnes of biomass, mainly wood, about five times the timber harvest that Britain could conceivably produce. To replace oil, the European Union has set a target of making 10 per cent of our transport fuel renewable by 2020, which will mean mainly biodiesel made from rape, soybean and imported palm oil. To replace gas, a gold rush of developers is trying to build anaerobic digesters on farms, where they will turn whole crops into methane.



All this is driven by subsidies that are mouth-wateringly generous to energy producers and eye-wateringly costly to consumers and drivers. According to the pressure group Biofuelwatch, the biomass power stations proposed for Britain would attract over £3bn a year through "renewable obligation certificates." Drax power station alone gets £43m a year to "co-fire" biomass alongside coal, much of it imported-for example in the form of olive pits, sunflower husks and peanut shells.



For all the furore that wind farms attract, bioenergy is a much bigger drain on the public purse than wind. Bioenergy currently supplies 83 per cent of all renewable energy used in Britain, while wind, solar, hydro, tide, wave, geothermal and heat pumps manage just 17 per cent, or 1 per cent of total energy. About half of that bioenergy is from waste incineration, sewage and landfill gas. The rest comes from timber or crops. The uncomfortable truth is that more than four-fifths of all "renewable" energy involves burning something.



If you mention biomass crops to an environmentalist, he or she will usually agree they are a bad thing-for reasons I will come to-but claim that they have little to do with the green movement, being driven instead by American electoral politics. (Iowa, a key state for presidential candidates to win early support, benefits from subsidies when the maize grown there is turned into ethanol.) Inconveniently for this thesis, the amount of Britain's primary energy supply from biomass (3 per cent) is about the same as America's (4 per cent).



It was not US politics that caused a subsidised wheat ethanol plant to open on Teesside in 2009 (and then close in May because the smell was a nuisance and the wheat price had become too high). As Robert Palgrave of Biofuelwatch says: "In America, bioenergy's supporters stress energy security; here the big driver has been climate change and in particular the European Union's Renewable Energy Directive."



Whether they admit it or not, the green movement caused this policy, the sole justification being to address climate change. Yet bioenergy is not just doing nothing to help cut carbon emissions- like wind; it is actually making the problem worse.



Here is why. A carbon atom is a carbon atom, wherever it comes from. Oxidise (burn) it and you get carbon dioxide. That is true whether it is in a hydrocarbon (like coal, oil or gas), a carbohydrate (like sugar in sugar cane or starch in maize), or a lipid (like oil from palm oil). Roughly one-third of the atoms we oxidise to liberate energy are carbon and two-thirds hydrogen. (Oxidised hydrogen is better known as water.)



As Jesse Ausubel of Rockefeller University has calculated, wood has a higher ratio of carbon to hydrogen (10) than coal (1), oil (0.5) and gas (0.25). Burn wood and you make 40 times more carbon dioxide for each unit of energy than if you burn gas. It's the worst thing you can do in carbon terms.



However, a carbon atom in wood was absorbed from the air a few years before when the tree grew, whereas a carbon atom in coal or gas was absorbed from the air hundreds of millions of years before. Since a felled tree can be fairly quickly replaced by a new one, wood is said by its supporters to be "carbon neutral" whereas gas is not.



The trouble with this argument is that it fails to take into account the fact that burning the timber oxidises carbon atoms decades before they would be released naturally. According to a report from Joanneum Research, this up-front carbon debt could take two or three centuries to be paid back in the case of timber. Harvesting also denies the carbon atoms to other species, such as beetles and woodpeckers (whereas almost nothing eats coal or gas).



In the case of crops grown for liquid fuel, a bigger problem emerges: the carbon oxidised in planting, harvesting, transporting and drying the grain turns out to be about as much as the carbon content of the plant itself. That is to say, almost as many carbon atoms (and almost as much energy) are burned in making the fuel as are in it. This is the case for maize grown for ethanol in the US, for example. By contrast drilling for, transporting and refining petrol has a 600 per cent energy gain.



Some biofuels are better. Brazilian sugar cane, which supplies a third of all fuel used by cars in that country, contains more carbon atoms than were burned in growing it. But don't celebrate too soon. The reason is that Brazilian sugar cane is mostly cut by poor labourers on piece rates, some of them children, rather than by machinery.



It gets worse. When a forest is felled to make way for a biofuel crop, the carbon stored in the trees and soil leaks into the atmosphere through decay. The crop is then grown with nitrogen fertiliser, some of which turns to nitrous oxide, a greenhouse gas 300 times more potent than carbon dioxide.



In Borneo vast areas of forest have been cleared to grow palm oil to make into biodiesel to sell to Europeans striving to meet their renewable targets. Much of this forest grew on waterlogged peat with high carbon content. When this is drained, the peat oxidises. Researchers at the University of Leicester have calculated that the carbon emissions from the drained peat are double the previous estimates of carbon emitted in the clearing of forests, so the policy of clearing forest for palm oil can "actually increase emissions relative to petroleum fuels." It would take 423 years to pay back the up-front carbon debt.



This is to say nothing of the orangutans whose habitat is eroded and fragmented. The European Environment Agency (EEA) says that "accelerated destruction of rainforest due to increasing biofuel production can already be witnessed."

Even if you do not clear rainforest to grow biofuels, you usually displace a food crop. This pushes up food prices, as a total of 17 independent reports have concluded. In August the UN Committee on World Food Security said biofuels had been a bigger cause of recent food price increases than the growth of the Asian middle class. The independent scholar Indur Goklany has estimated that biofuels killed 192,000 people in 2010 by increasing hunger.



Higher prices encourage farmers to cultivate more virgin land, so biofuels encourage the destruction of rainforest to grow food, even if they did not directly replace forest. Such "indirect land use change" is impossible to measure. The European Commission promised to come up with an estimate, but in September Reuters obtained a leaked report in which the commission admitted it could not put a number on the problem. A few days later the EEA issued a statement that because biofuels displace food crops, the assumption that they are carbon neutral is "not correct."



An American study published in Science in 2008 concluded that because maize made into ethanol could not be exported as food, some virgin land would be cleared and ploughed elsewhere in the world for every acre of ethanol maize grown, which meant that ethanol had effectively double the carbon footprint of petroleum.



Britain gets most of its biofuel from Argentinian soybeans. A recent report commissioned by the Department of Energy and Climate Change concluded that if bioenergy grows to 20 per cent of primary energy by 2020 as envisaged, we will be importing 67 per cent of it. So not only is the impact on hunger and rainforest destruction directly on our conscience; there is also no prospect of energy security from bioenergy. This import dependence is causing second thoughts about how "sustainable" Britain's rush to biomass really is, and that is frightening off the banks that would need to lend to such projects.



At this point, biofuel's supporters argue that the second generation of biofuels, consisting of "cellulosic" miscanthus grass and jatropha plants, will be grown on marginal land not used for farming and not covered in rainforest. When asked where this land is, and how it can be made fertile enough to grow biofuels, they point to degraded and abandoned farmland. The trouble is, they forgot to tell the people who live there. Göran Berndes of Chalmers University of Technology in Sweden co-authored a report that studied 17 bioenergy feasibility studies. Its conclusion was that "land reported to be degraded is often the base of subsistence for the rural population."



In Andhra Pradesh, Berndes did find that jatropha planting helped retain water and didn't prevent land being grazed, so its impact was "generally positive, creating a complementary source of income to the farmers." But elsewhere things are not so rosy. Fatou Mbaye, food rights co-ordinator for Action Aid Senegal, told the New Internationalist recently: "At first, we were told that [jatropha] would be grown on marginal land. But it's being grown on the best arable land with the highest rainfall, or where good irrigation is possible, to make it economically profitable."

While the impact of bioenergy on food prices has been severe, the reduction in oil use has been minuscule. In 2010, America turned 40 per cent of its maize crop into fuel, displacing just 3 per cent of its oil consumption. Worldwide, 5 per cent of grain was turned into fuel, displacing just 0.6 per cent of oil. To cut say 20 per cent of world oil use would require such a gigantic land grab that starvation would be widespread and rainforest a distant memory.



The land grab is huge because of bioenergy's low power density. According to Jesse Ausubel, an American ethanol farm generates about 0.047 watts per square metre, once the energy inputs are deducted; a New England forest can provide wood at the rate of about 0.1 watts per square metre; and a Brazilian sugar cane field, ignoring human toil, manages about 3.7.



The energy expert Vaclav Smil of the University of Manitoba says a realistic estimate of the energy density of bioenergy worldwide is less than 0.5 watts per square metre. The world economy uses energy at the rate of 15,000 gigawatts (474 exajoules per year). To supply that from bioenergy would require 30 million square km, a territory the size of China, Brazil, India and Australia put together. Or "Renewistan" as engineer Saul Griffith calls this fabled land.



The champions of biofuels are left with one card to play: algae. In theory, by growing algae in closed bioreactors in salty water in sunny places, you can achieve much higher power densities. In practice, many engineering hurdles remain before first-generation algal farms go commercial.



The conclusion is stark. There is no way to run even a fraction of the world economy on bioenergy without severely damaging the planet. For the environment's sake we must use a much denser form of energy, such as fossil fuel or nuclear, whose footprints I estimate to be about 100 and 10,000 times smaller than biofuel's respectively. The same applies to other forms of renewable energy, with the possible exception of solar power, whose density could one day be better than the rest (except in cloudy Britain). So by all means install a wood-burning stove or use biodiesel in your car. But don't pretend you are doing the planet a favour.



A declaration of interest. As a landowner I benefit from the recent increases in prices of wheat and wood caused by bioenergy. Recently I turned down a proposal to establish an anaerobic digester on my farm, even though it would have guaranteed a good income. So the views expressed here are against my financial interest.