France harvests miscanthus for energy

Name: Miscanthus giganteus ('elephant grass', 'e-grass'). Origin: Asian grasslands. Use: ideal energy crop for the production of green electricity, heat and bioproducts. Remark: follows C-4 path during photosynthesis.

For the first time, France has harvested the promising biofuel crop as part of a commercial enterprise. Together with farmers from Bretagne, the company Bical France has gone beyond the experimental phase and is now harvesting the tall grass that will be used as a biomass feedstock in a series of industries:

• combustion in biomass power plants (co-fired with coal or as a single feedstock)
• second generation ethanol
• production of particle boards
• bioplastics feedstock
• environmentally friendly building materials

Miscanthus giganteus could play a major role in the development of a biomass energy industry around the world, and several initiatives with that aim are underway (see earlier post). In France, trials with a first batch of 500 tons of the tall, rapidly growing grass species, that was harvested mechanically on 40 hectares of land in Bretagne have been completed. Average yields for the energy crop were 12.5 tons/hectare but depending on the maturity of the plant and the climate, it can attain average yields of up to 20tons/ha (mainly in the tropics and subtropics).

Cooperative organisation
The plantation was created in 2004 by Bical France, a daughter of Biomass Industrial Crops Ltd which has already produced 400,000 tons of the crop in the UK. The company which was formed by British farmers in 1998 is the main European supplier of industrial miscanthus (amongst a dozen smaller companies). The company's turnover in 2005 was €6 million. In order to get a hold in France, Bical contracted local farmers in Bannalec, in the Finistère region, and in Voves, in the Eure-et-Loire region.

"We work in a cooperative system. All the member-producers retain a part of Bical France's capital. We wish to see them obtaining a regular and decent income from the venture", explains Emmanuel Maupeou, general director.

An astonishing energy content
The first batch of miscanthus was bought by a leader of an energy-intensive industry, the cement group Lafarge Ciments, which was seduced by the impressive calorific content of the elephant grass -- it is considerably higher than most kinds of woody biomass. The 'lower heating value' (LVH) of the grass is around 4700kWh/ton, compared to 3300 for woody biomass, which makes it a very profitable bioenergy feedstock.

Created in Asia from Miscanthus sinensis and Miscanthus sacchariflorus, the hybrid can replace up to 50% of all coal used in an average coal-fired power plant, without the need for any modifications of the plant. It can be used in dedicated biomass power plants as a single feedstock, as well as in smaller but highly efficient Combined Heat and Power systems and in ordinary biomass boilers for homes.
When miscanthus is burned, it emits less CO2, because the grass stores the bulk of its carbon in its rhizomes, the underground roots that allow it to renew itself. In a sense, elephant grass temporarily acts as a carbon sink because only the biomass above the ground is harvested. This makes it an interesting crop for power producers and industries that want to reduce their carbon emissions and receive carbon credits for doing so.

Before the arrival of Bical France, miscanthus was only cultivated in the context of scientific experiments and research:
biomass :: bioenergy :: biofuels :: energy :: sustainability :: France :: ethanol :: miscanthus ::elephant grass ::


But now it has attained a phase where commercial use becomes viable and several European countries are starting to invest in the biomass source. Together with the Roubaix based company Kalys, the French Institut National de la Recherche Agronomique (Inra) has established full-scale plantations and has studied ways to reduce the production costs involved in cultivating miscanthus. Its conclusions: the grass can be grown both in greenhouses as well as in open fields, and remain economically competitive under both systems.

No pests, no diseases
A plantation of elephant grass does need a considerable amount of financial and human means, though, because even though it can be harvested mechanically, planting has to be done manually. The soil in which the grass thrives must be aerated and beds must be created by hand. In the first year, growth-threatening herbs have to be removed from the field for the miscanthus to take root and in order to ensure that the grass's rhizomes establish themselves in such a way that they propagate new shoots in the years thereafter. Bad herbs may be removed by hand, but appropriate herbicides do the job too, because miscanthus is quite strong and resistant to chemical treatment. Bical chose for the latter option:

"We use a herbicide during the first year only, because from year 2 onwards, the leaves of the elephant grass become dry at the beginning of the winter and fall off, covering the soil, where they form a rich layer of natural nutrients that prevents bad herbs from growing", explains the general director. "Nor do we use fungicides or insecticides because there is no disease or pest associated with miscanthus".

"Moreover, fields of elephant grass harbor many animal species because the tall grass protects their nests from the rainy season that arrives in March, when the soil is dry or still frozen. As a perennial crop, the grass renews itself naturally and can be harvested over a period of 5 to 18 years. It can grow to a height of 4 metres. And because it is sterile, there is no risk of unwanted dissemination."

Psychological barriers
Even if the qualities of are beginning to be recognized, there is still a lot working against its widespread use: the production cost, the competition of other biomass sources and energy crops, and the difficulty of convincing farmers of adopting a new species... But for Emmanuel de Maupeou, the principal barrier against the development of miscanthus as a basic energy crop is "psychological": "a certain number of environmentalists disapprove of the arrival of a new, non-indigenous plant sepcies, but they forget that this was also the case for maïze and the common potato."

More information:
Novethic.fr - media en ligne du dévelopement durable: Le miscanthus, combustible biomasse prometteur
Bical France: environmental aspects of miscanthus as a bioenergy crop [*pdf]
BioMatNet: European Concerted Action on Miscanthus - leaflet and report

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Flex-fuel vehicles in Brazil hit 2 million mark, make up 77% of the market

According to the Associação Nacional dos Fabricantes de Veículos Automotores, Brazil's new generation of cars and trucks adapted to run on ethanol (alcohol) has just hit the two-million mark. 'Flex-fuel' vehicles, which run on any combination of ethanol and petrol, now make up an impressive 77% of the Brazilian market. Volkswagen and Fiat vie for the first place and both car manufacturers produced and sold around 200,000 flex-fuel vehicles in the first 6 months of this year.

Ethanol-driven cars have been on sale in Brazil for 25 years, but they have been enjoying a revival since flex-fuel models first appeared in March 2003. Just 48,200 flex-fuel cars were sold in Brazil in 2003, but the total had reached 1.2 million by the end of last year and had since topped two million, the Brazilian motor manufacturers' association Anfavea said. (Statistics for the type and number of cars produced and sold in Brazil in the year 2006, please visit this page).

Brazil began its Pro-Alcohol programme more than 20 years ago to promote the use of ethanol as an alternative fuel for cars. At the time, Brazil had a military government, which wanted to reduce the country's dependence on imported Middle Eastern petroleum after the 1970s oil shocks. The idea fell out of favour in the 1990s after sugar prices rose and the price of oil fell, while Brazil's state oil company Petrobras discovered new offshore oilfields which reduced the need for imports.

But in 2003, a new generation of cars capable of running on alcohol entered production, thanks to a combination of new technology and tax breaks. "Flex-fuel" cars attract a purchase tax of 14%, while buyers of their exclusively petrol-powered counterparts are charged 16%:

ethanol :: biodiesel :: biomass :: bioenergy :: biofuels :: energy :: sustainability :: Brazil :: flex-fuel ::

As oil prices continue to hover near the $70-a-barrel mark, amid fears that the world may soon run out of fossil fuels, carmakers and politicians alike are desperate to come up with alternative ways to power the world's motor vehicles. Even a man as closely linked with the oil industry as President George W Bush is now spreading the message that one day we may be growing our fuel instead of digging it out of the ground.

"An interesting opportunity, not only for here but for the rest of the world, is biodiesel, a fuel developed from soybeans," he said in June last year. For the owners of today's polluting gas-guzzlers, it is easy to see this as something for the far-distant future, an irrelevance that will not affect their lives for many years to come.

But in Brazil, it is already a reality.

In the mid-1980s - before any other country even thought of the idea - Brazil succeeded in mass-producing biofuel for motor vehicles: alcohol, derived from its plentiful supplies of sugar-cane. Differently-powered cars were actually in the majority on Brazil's roads at the time, marking a major technological feat.

But the programme that had put the country so far ahead was very nearly consigned to history when oil prices slid back from the high levels seen in the 1970s. Alcohol-powered cars fell out of favour and languished in obscurity until two years ago, when production picked up again in a big way. Now Brazilians are flocking to buy cars that give them the chance to mix and match alcohol with regular fuel - and conventional motor vehicles that run purely on petrol are looking old-fashioned once again.

Military-inspired

Brazil's state-run alcohol fuel programme was set up for patriotic, not financial or environmental reasons. The military government that ran the country from 1964 to 1985 wanted to reduce its dependence on Middle Eastern petroleum during the 1970s oil crisis.

The technology was far from new, having been around since the 1920s, but no country had employed it on such a scale. Under the Pro-Alcohol programme, farmers were paid generous subsidies to grow sugar-cane, from which ethanol was produced.

The price at the pump was also subsidised to make the new fuel cheaper than petrol, while the motor industry turned out increasing numbers of vehicles adapted to burn pure ethanol. As a result, in 1985 and 1986, more than 75% of all motor vehicles produced in Brazil - and more than 90% of cars - were designed for alcohol consumption.

But then it all went wrong.

Backlash hits

A combination of factors turned the tide against ethanol:

* Under newly-restored civilian rule, governments were less concerned about promoting the fuel for national security reasons

* Sugar prices rose, making the ethanol subsidy too costly for the state

* Oil prices had fallen from their 1970s highs

* State oil company Petrobras had discovered new offshore oilfields, making Brazil more self-sufficient in oil.

There remained the environmental argument in favour of ethanol: unlike petrol, it is free of pollutants such as sulphur dioxide, while the carbon dioxide emissions it produces can be cancelled out by growing another sugar-cane plant. And in one lasting benefit, ethanol had already replaced lead in conventional Brazilian petrol, putting paid to the worst kind of airborne pollution.

But despite ethanol's green credentials, Brazilian enthusiasm for the fuel reached its lowest ebb in 1997, just as the world was marking five years since Rio de Janeiro hosted the United Nations Earth Summit. That year, just 1,075 motor vehicles built to run on alcohol rolled off the country's production lines - a mere 0.06% of the total output.

Competition

It was at that very point that the US started to show interest in biofuels, as the authorities in California and other states passed laws forcing car manufacturers to reduce pollution levels. The US now produces nearly as much ethanol as the Brazilians do, although the raw material it uses is maize rather than sugar-cane, while President Bush's biodiesel made from soybeans offers another alternative to petroleum.

But Brazilian producers maintain their ethanol is still cheaper to produce - and their market has now received fresh impetus from a combination of tax breaks and technological advancement. A new generation of alcohol-powered cars entered production in Brazil in 2003, after the government decided that cars capable of burning ethanol should be taxed at 14%, instead of 16% for their exclusively petrol-powered counterparts.

Unlike earlier models, these are "flex-fuel" cars - equally happy with pure alcohol, pure petrol, or any blend of the two. When the fuel tank is filled, a special computer chip analyses the mixture and adjusts the motor according to how much ethanol and how much petrol it contains.

In 2004, the first full year that "flex-fuel" cars were on sale, they accounted for more than 17% of the Brazilian market. Last year, they scored an even bigger success, overtaking petrol-driven models for the first time since the 1980s and taking 53.6% of the market for new cars.

But in the wake of the US, other countries are beginning to discover the wonders of crop-based motor fuel - and Brazil has a fight on its hands if it wants to remain the world leader in the field.

More information:

Tribuna de Alagoas: Brasil produziu 2 milhões de carros flex

A Tarde On Line: Venda de veículos flex no Brasil alcança 2 milhões de unidades

BBC: The rise, fall and rise of Brazil's biofuel

BBC: Brazil's alcohol cars hit 2m mark

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OPEC president downplays ethanol but Brazilian counterpart disagrees

Quicknote ethanol potential
A few days ago we reported about Edmund Daukoru's visit to Brazil's ethanol producing regions. The president of the Organization of Petroleum Exporting Countries on Thursday reiterated his interest in Brazilian ethanol technology, but downplayed the future role of the biofuel in the world's energy matrix. Daukoru, who is also Nigeria's oil minister, was visiting ethanol installations in Piracicaba, Sao Paulo state.

"Nigeria currently is working to create a reliable ethanol market together with local private companies," Daukoru said. Yet, he added that at first, Nigeria was interested in the usage of ethanol for the energy matrix of companies, and not yet as gasoline additive. Asked what the role of ethanol in the global energy matrix will be in 10 or 20 years, Daukoru said that although its importance will grow, it will likely only play a minor role.

"In terms of actual percentages, it will still be a minor component," Daukoru said. "I would not see a very dramatic percentage that will be met by bioethanol. I think it will remain modest, small to modest."

Despite downplaying the future role of ethanol, just the presence of the OPEC president in Brazil's main sugar cane- and ethanol-producing region already had a major importance, said Jaime Finguerito, head of research and development at the cane technology center in Piracicaba.

"It shows that ethanol gets the respect of the most important representative of the global petroleum industry," Finguerito said. Finguerito added that Daukoru told him that the oil price was unlikely to fall below $30 a barrel again, which would make an international ethanol market viable.

Brazil is the world's biggest exporter of ethanol, and its second-biggest producer. Daukoru is heading a committee for the implementation of an ethanol program in his country, which is supported by Brazil's state-run oil firm Petroleo Brasileiro SA (PBR), or Petrobras.

The Brazilian oil company plans to export ethanol made from sugarcane to Nigeria, while at the same time helping the African country to build its own ethanol industry. Petrobras Downstream Director Paulo Roberto Costa told Dow Jones Newswires in July that the company plans to start ethanol shipments to Nigeria in August or September.

Daukoru on Thursday made no comment on possible ethanol shipments to Nigeria, and emphasized that his main interest was the transfer of Brazilian ethanol technology to the African country. Daukoru went on to visit an ethanol plant in Piracicaba run by Brazil's only publicly traded sugar and ethanol company Cosan SA.

For a more extensive analysis of the OPEC president's visit, see: ANBA: The whole world is going to mix alcohol into petrol, said the Opec president - August 18, 2006

[Entry ends here].
ethanol :: biomass :: bioenergy :: biofuels :: energy :: sustainability :: :: Brazil :: Nigeria :: OPEC ::

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Terra preta: how biofuels can become carbon-negative and save the planet

Most often, biofuels are seen as being 'carbon- neutral' in that they do not add CO2 to the atmosphere. When they are burned for energy, CO2 is emitted, but it gets taken up again as the new biomass grows, thus closing the carbon cycle and resulting in a neutral balance. This is the commonly held view of how biofuels are 'green'. In an early text, however, we hinted at the possibility of bioenergy doing even more by becoming truly carbon-negative: while using it as a source of energy, make it work as a carbon sink at the same time (in dutch: Bioenergie: brug naar een post-petroleumtijdperk? [*.pdf]).

How could this be achieved? It could be done by storing more carbon underground than gets released during the use of the fuels. The way to do so would rely on a technique known as terra preta ('black earth') which is thousands of years old. Ancient civilizations in Latin America and West Africa already used it in forest agriculture, but scientists are still baffled by its effectiveness. And they are trying to find out how it works exactly. It could be the ultimate natural and green carbon sequestration technique. Moreover, there is profit to be made from it. Terra preta not only stores carbon (for which credits with a real monetary value exist today), the rich black earth also boosts crop yields in a spectacular manner.

The ultimate carbon capture technique
Commonly proposed carbon sequestration strategies face some major hurdles. Technical 'geosequestration' methods consist of pumping large amounts of CO2 deep underground. But these techniques are still under development, and recent evidence suggests that CO2 leakage forms a major problem and could in fact worsen matters.

On the other hand, natural methods that store carbon in living ecosystems may be possible in the short term but require huge swathes of land and are only as stable the ecosystems themselves. These strategies would come down to planting biomass and leaving it untouched.

An ideal solution, in particular for tropical countries, would consist of combining the quick fix of biological methods with the absolute potential of technical ones, while deriving energy from doing so. Terra preta may offer exactly the basis for such a strategy, as a recent article in Nature reveals.

Mystery in the jungle
'Amazonian Dark Earth', or terra preta do indio, has mystified science for the last hundred years. Three times richer in nitrogen and phosphorous, and twenty times the carbon of normal soils, terra preta is the legacy of ancient West African societies and Amazonians who pre-date Western civilization. Scientists who long debated the capacity of 'savages' to transform the virgin rainforest now agree that indigenous people transformed large regions of the Amazon and the West African rainforest into amazingly fertile black earth. Most tropical soils are so-called oxisols that are poor in nutrients and often suffer under aluminum-toxicity (hence their reddish color). Terra preta transforms those soils into black nutrient-rich beds that boost crop yields [picture]. The indigenous techniques remain enigmatic but are believed to have consisted of slash-and-smolder to lock half of the carbon in burnt vegetation into a stable form of bio-charcoal, instead of releasing the bulk of it into the atmosphere like typical slash-and-burn practices.

The difference between terra preta and ordinary soils is immense. A hectare of meter-deep terra preta can contain 250 tonnes of carbon, as opposed to 100 tonnes in unimproved soils from similar parent material, according to Bruno Glaser, of the University of Bayreuth, Germany (Terra Preta website). To understand what this means, the difference in the carbon between these soils matches all of the vegetation on top of them. Furthermore, there is no clear limit to just how much 'biochar' can be added to the soil. Claims for biochar's capacity to capture carbon sound almost audacious. Johannes Lehmann, soil scientist and author of Amazonian Dark Earths: Origin, Properties, Management, believes that a strategy combining biochar with biofuels could ultimately offset an incredible 9.5 billion tons of carbon per year -- an amount equal to the world's total current fossil fuel emissions!

Obviously then, there is profit to be made in this black earth, for if green is the new black, then black could be the new green:

bioenergy :: biofuels :: energy :: sustainability :: CO2 :: carbon sequestration :: charcoal :: terra preta


Biofuels are touted as 'carbon neutral', but biofuels and biochar together promise to be 'carbon negative'. Danny Day, the founder of a company called Eprida is already putting these concepts into motion with systems that turn farm waste into hydrogen, biofuel, and biochar.

The Eprida technology uses agricultural waste biomass to produce hydrogen-rich bio-fuels and a new restorative high-carbon fertilizer (ECOSS) ...In tropical or depleted soils ECOSS fertilizer sustainably improves soil fertility, water holding and plant yield far beyond what is possible with nitrogen fertilizers alone. The hydrogen produced from biomass can be used to make ethanol, or a Fischer-Tropsch gas-to-liquids diesel (BTL diesel), as well as the ammonia used to enrich the carbon to make ECOSS fertilizer.

We don't maximize for hydrogen; we don't maximize for biodiesel; we don't maximize for char... By being a little bit inefficient in each, we approximate nature and get a completely efficient cycle.

Terra preta's full beauty appears in this closed loop. Unlike traditional sequestration rates that follow diminishing marginal returns-aquifers fill up, forests mature-practices based on terra preta see increasing returns. Terra preta doubles or even triples crop yields. More growth means more terra preta, begetting a virtuous cycle. While a global rollout of terra preta is still a ways away, it heralds yet another transformation of waste into resources.

How ironic it is that ancient humans cultivated the very fertility of Earth's most pristine places so seamlessly as to be nearly invisible. Perhaps then our challenge as planetary gardeners is not to preserve nature in a bubble but to reweave ourselves into it-to invert our footprints into handprints.

[Entry ends here]

Resources:

-Bruno Glaser's Terra Preta website at the University of Bayreuth.
-Johannes Lehmann's Terra Preta de Indio website at the dept. of Soil Biogeochemistry, Cornell University.
-A special Symposium during the 2006 Annual Meeting of the American Academy for the Advancement of Science (AAAS) in St. Louis on "Amazonian Dark Earths - New Discoveries" received wide press coverage. Read here.
-Worldchanging: Terra Preta: Black is the New Green

Given the importance of this topic for our project, we add the original article in full below. Copyright, Nature.

Putting the carbon back: Black is the new green
Nature 442, 624-626 (10 August 2006)

One way to keep carbon dioxide out of the atmosphere is to put it back in the ground. In the first of two News Features on carbon sequestration, Quirin Schiermeier asked when the world's coal-fired power plants will start storing away their carbon. In the second, Emma Marris joins the enthusiasts who think that enriching Earth's soils with charcoal can help avert global warming, reduce the need for fertilizers, and greatly increase the size of turnips.

In 1879, the explorer Herbert Smith regaled the readers of Scribner's Monthly with tales of the Amazon, covering everything from the tastiness of tapirs to the extraordinary fecundity of the sugar plantations. "The cane-field itself," he wrote of one rum-making operation, "is a splendid sight; the stalks ten feet high in many places, and as big as one's wrist." The secret, he went on, was "the rich terra preta, 'black land', the best on the Amazons. It is a fine, dark loam, a foot, and often two feet thick."

Last month, the heirs to Smith's enthusiasm met in a hotel room in Philadelphia, Pennsylvania, during the World Congress of Soil Science. Their agenda was to take terra preta from the annals of history and the backwaters of the Amazon into the twenty-first century world of carbon sequestration and biofuels.

They want to follow what the green revolution did for the developing world's plants with a black revolution for the world's soils. They are aware that this is a tough sell, not least because hardly anyone outside the room has heard of their product. But that does not dissuade them: more than one eye in the room had a distinctly evangelical gleam.

The soil scientists, archaeologists, geographers, agronomists, and anthropologists who study terra preta now agree that the Amazon's dark earths, terra preta do índio, were made by the river basin's original human residents, who were much more numerous than formerly supposed. The darkest patches correspond to the middens of settlements and are cluttered with crescents of broken pottery. The larger patches were once agricultural areas that the farmers enriched with charred trash of all sorts. Some soils are thought to be 7,000 years old. Compared with the surrounding soil, terra preta can contain three times as much phosphorus and nitrogen. And as its colour indicates, it contains far more carbon. In samples taken in Brazil by William Woods, an expert in abandoned settlements at the University of Kansas in Lawrence, the terra preta was up to 9% carbon, compared with 0.5% for plain soil from places nearby1.

From Smith's time onwards, the sparse scholarly discussion of terra preta was focused mainly on the question of whether 'savages' could have been so clever as to enhance their land's fertility. But Woods' comprehensive bibliography on the subject now doubles in size every decade. About 40% of the papers it contains were published in the past six years.

Loam ranger
The main stimulus for this interest was the work of Wim Sombroek, who died in 2003 and is still mourned in the field. Sombroek was born in the Netherlands in 1934 and lived through the Dutch famine of 1944 — the Hongerwinter. His family kept body and soul together with the help of a small plot of land made rich and dark by generations of laborious fertilization. Sombroek's father improved the land in part by strewing it with the ash and cinders from their home. When, in the 50s, Sombroek came across terra preta in the Amazon, it reminded him of that life-giving 'plaggen' soil, and he more or less fell in love. His 1966 book Amazon Soils began the scientific study of terra preta.

Since then trial after trial with crop after crop has shown how remarkably fertile the terra preta is. Bruno Glaser, of the University of Bayreuth, Germany, a sometime collaborator of Sombroek's, estimates that productivity of crops in terra preta is twice that of crops grown in nearby soils2. But it is easier to measure the effect than explain it through detailed analysis.

Everyone agrees that the explanation lies in large part with the char (or biochar) that gives the soil its darkness. This char is made when organic matter smoulders in an oxygen-poor environment, rather than burns. The particles of char produced this way are somehow able to gather up nutrients and water that might otherwise be washed down below the reach of roots. They become homes for populations of microorganisms that turn the soil into that spongy, fragrant, dark material that gardeners everywhere love to plunge their hands into. The char is not the only good stuff in terra preta — additions such as excrement and bone probably play a role too — but it is the most important factor.

Leaving aside the subtleties of how char particles improve fertility, the sheer amount of carbon they can stash away is phenomenal. In 1992, Sombroek published his first work on the potential of terra preta as a tool for carbon sequestration3. According to Glaser's research, a hectare of metre-deep terra preta can contain 250 tonnes of carbon, as opposed to 100 tonnes in unimproved soils from similar parent material. The extra carbon is not just in the char — it's also in the organic carbon and enhanced bacterial biomass that the char sustains.

Ground control
That difference of 150 tonnes is greater than the amount of carbon in a hectare's worth of plants. That means turning unimproved soil into terra preta can store away more carbon than growing a tropical forest from scratch on the same piece of land, before you even start to make use of its enhanced fertility. Johannes Lehmann of Cornell University in Ithaca, New York, has studied with Glaser and worked with Sombroek. He estimates that by the end of this century terra preta schemes, in combination with biofuel programmes, could store up to 9.5 billion tonnes of carbon a year — more than is emitted by all today's fossil-fuel use4.

Mud pack
The year before he died, Sombroek helped to round up like-minded colleagues into the Terra Preta Nova group, which looks at the usefulness of using char in large-scale farming and as a carbon sink. The group was well represented at the Philadelphia meeting, although Glaser was not there. Their aim is to move beyond the small projects in which many of them are involved and find ways of integrating char into agribusiness. After all, wherever there is biomass that farmers want to get rid of and that no one can eat, char is a possibility. That means there are a lot of possibilities.

One problem is that there is a new competitor for farm waste. Plant are largely made up of cellulose, indigestible material in cell walls. Recent technological advances make it likely that quite a lot of that cellulose might be turned into biofuel. At the moment, ethanol is made from corn in the United States and from sugar in Brazil; if it were made directly from cellulose, producers could work with a wider range of cheaper biomass. Given the choice of turning waste material into fuel or into charcoal, farmers might be expected to go for fuel, especially if that is the way that policy-makers are pushing them: US President George W. Bush promised $150 million for work on cellulosic ethanol in his 2006 state of the union speech.

But Lehmann and his colleagues don't see biofuel as an alternative to char — they see the two developing hand in hand. Take the work of Danny Day, the founder of Eprida. This "for-profit social-purpose enterprise" in Athens, Georgia, builds contraptions that farmers can use to turn farm waste into biofuel while making char. Farm waste (or a crop designed for biofuel use) is smouldered — pyrolysed, in the jargon — and this process gives off volatile organic molecules, which can be used as a basis for biodiesel or turned into hydrogen with the help of steam. After the pyrolysation, half of the starting material will be used up and half will be char. That can then be put back on the fields, where it will sequester carbon and help grow the next crop.

Negative thinking
The remarkable thing about this process is that, even after the fuel has been burned, more carbon dioxide is removed from the atmosphere than is put back. Traditional biofuels claim to be 'carbon neutral', because the carbon dioxide assimilated by the growing biomass makes up for the carbon dioxide given off by the burning of the fuel. But as Lehmann points out, systems such as Day's go one step further: "They are the only way to make a fuel that is actually carbon negative".

Day's pilot plant processes 10 to 25 kg of Georgia peanut hulls and pine pellets every hour. From 100 kg of biomass, the group gets 46 kg of carbon — half as char — and around 5 kg of hydrogen, enough to go 500 kilometres in a hydrogen-fuel-cell car (not that there are many around yet). Originally, Day was mostly interested in making biofuel; the char was just something he threw out, or used to make carbon filters. Then he discovered that his employees were reaping the culinary benefits of the enormous turnips that had sprung up on the piles of char lying around at the plant. Combining this char with ammonium bicarbonate, made using steam-recovered hydrogen, creates a soil additive that is now one of his process's selling points; the ammonium bicarbonate is a nitrogen-based fertilizer.

"We don't maximize for hydrogen; we don't maximize for biodiesel; we don't maximize for char," says Day. "By being a little bit inefficient with each, we approximate nature and get a completely efficient cycle." Robert Brown, an engineer at Iowa State University in Ames, has a $1.8-million grant from the United States Department of Agriculture (USDA) to fine-tune similar technology, although being in Iowa, he uses corn stalks not peanut hulls. "We are trying an integrated approach: we are trying to evaluate the agronomic value, the sequestration value, the economic value, the engineering," he says.

Brown thinks a 250-hectare farm on a char-and-ammonium-nitrate system can sequester 1,900 tonnes of carbon a year. A crude calculation on that basis suggests the US corn crop could sequester 250 million tonnes of carbon a year. At the moment, no one knows how long this could go on; no one has yet found a ceiling for char addition.

Stephen Joseph of Biomass Energy Services and Technology in New South Wales has built a number of char-producing machines in Australia that work at fairly large scales (the models have grown from an original 'Piglet' through a larger 'Daisy' to a positively bullish 'El Toro'). Joseph looks for companies with a waste problem such as a paper mill with spare scraps or a dairy with old bedding and manure, and then integrates char production into the business so that the heat produced in pyrolysis is used where the firm needs it.

So far, Joseph's company is being brought in to solve waste-management problems, but he hopes the value of the char will become a selling point in itself. For that to happen, however, he needs some help. His machines can be tuned to make char of various sorts: different sized particles with different sized pores and different amounts of other elements. Which is the best? It's a question he asks in Philadephia, and one of the things that Brown's research in Iowa aims to find out.

The right protocol
Such technical unknowns are not the only obstacles on the road to a black revolution. One problem is that the purported benefits of char do not slot easily into the framework of the Kyoto Protocol, an international agreement to reduce carbon emissions. Lehmann hopes to see the process get going under the aegis of the protocol's Clean Development Mechanism, in which rich countries sponsor green projects in poor countries and get credit for the reduced emissions. To this end, he is amassing evidence that modern char techniques can actually keep the carbon involved locked up for centuries. His Cornell colleague John Gaunt is working on ways to present the technique as the sort of 'change in practice' that could count as a tradeable carbon-emission reduction of the sort allowed under Kyoto.

Then there are your risk-averse farmers. They haven't heard of char. And they aren't going to buy it — let alone buy a strangely named machine to make it — unless they know it will make them money. It is no good pitching it to them with a mouthful of scientific caveats about not knowing the right kind of char for each type of soil or exactly how it works. You have to be able to sell specific benefits and real attractions. "A lot of farmers are environmentalists," says John Kimble, a USDA man who has just retired from the National Soil Survey Center in Lincoln, Nebraska. "But they look at the bottom line, as we all do."

After the afternoon coffee break in Philadelphia, Kimble takes the podium and the wind out of everyone's sails. He is sympathetic to the terra pretans goals — indeed he was a good friend of Sombroek's — but that doesn't stop him asking hard questions. "Can you do this in a no-till way?" is one tricky query. Kimble and many others have been pushing no-till farming, which basically means doing without ploughs, as a partial solution to erosion, pesticide run-off and fuel costs. The idea is that the less you mess with the soil, the less its components separate and wander away. But biochar is light and fine, like the black grit left in a barbecue. If you don't physically insert it into the soil, it might just blow away.

Everyone listens politely. But while watching their responses, it was hard not to worry that the same enthusiasm that has brought them together might also trap them in a cul de sac. They obviously respect economics and pragmatic requirements. But these are not people principally moved by practical politics or bottom lines; they are people moved by ideals. They start from the basis that the answer lies in the soil, more or less whatever the question is, and can't quite understand why this isn't self-evident to everyone else. Faced, for example, with the suggestion that all corn matter be turned into ethanol, they tend simply to say "Well it could be — but we hope, of course, it will go into the soil." They know they ought to be marketing terra preta as a resource, or a policy instrument; but they can't stop seeing it as a wonder.

Policy is not always, or even often, dictated by pure rationality. Perhaps terra preta's compelling history and rich, earthy smell will go to the heads of that diffuse band of policy-makers who hand out the cash. The enthusiasts need to be more down to earth; but the policy people might benefit from getting their hands dirty.

References:
1. Woods, W. I. & McCann, J. M. in Yearbook Conf. Latin Am. Geogr. Vol. 25 (ed. Caviedes, C.) 7–14. (Univ. Texas, Austin, 1999).
2. Glaser, B. Phil. Trans. R. Soc. (in the press).
3. Sombroek, W. G. Interciência 17, 269–272 (1992).
4. Lehmann, J. , Gaunt, J. & Rondon, M. Mitigation Adapt.Strateg. Global Change 11, 403–427 doi:10.1007/s11027-005-9006-5 (2006).

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