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Biochar: The key to Carbon-Negative Biofuels

The world is losing its battle against global warming. Even in Europe, where they have valiantly fought to reduce greenhouse gas emissions, the imbalance gets worse every day. Biofuels are the biggest disappointment. They still emit CO2 when burned and require fertilizer, processing and transportation which all emit even more CO2. The justification for biofuels is that the growing plants take CO2 out of the air. However, plants growing on the land before planting were already capturing CO2, so only the increase in CO2 capture (if any) should be counted

The natural balance of the earth has always included carbon storage in the plants and soil. The problem is that we have disrupted that balance. We have burned in one century much of the carbon that nature sequestered over millions of years. Coal is almost pure carbon, gathered by plants and sequestered by natural processes. We need to stop burning it!

Though growing plants take CO2 from the air and fix it in their cells, the carbon is only borrowed: 99% of that carbon ends up back in the atmosphere as the plant is eventually burned or consumed by animals, termites, funguses, nematodes or worms which then return the carbon to the atmosphere. Pyrolysis is a way to grab the carbon in plants before it can become a meal for these creatures and return it to the soil as pure carbon biochar.

Pyrolysis mimics the natural process that turned ancient plants into coal: When biomass is heated up with no oxygen supply it melts into carbon, syngas and biooil. Pyrolysis was used thousands of years ago by the natives of Brazil to enrich their poor, acidic soil into Terra Preta, one of the richest, most productive soils known to man.

Terra Preta still contains as much as 9% carbon. It is always found with pottery shards and other evidence that it was man made. It is so productive that it is bagged up and sold today as potting soil. We’re still trying to match their superb results. If we succeed, we will solve world hunger, global warming and our energy shortage in one stroke.

The Amazon culture that made these soils was killed by conquest and disease. The primitive people in the area today practice slash and burn agriculture, which quickly depletes the soil and spews CO2 and pollutants into the atmosphere. The Terra Preta was created by slash and char, which involves cutting off oxygen to the burning biomass by covering it with dirt. Without oxygen, little CO2 is produced and the biomass melts into carbon with a very fine structure called biochar. The hydrogen in the plant molecules produces heat and water as it combines with oxygen from the plant molecules.

The buried biochar is like activated charcoal with very high surface area. It can hold water and nutrients and gradually release them as needed. Even more important, the nanoscale structure of biochar, like a coral reef, hosts a whole ecosystem of soil fungi and bacteria that feeds the roots of plants. This part of the terra preta story is still not fully understood. It takes some time for this microscopic biological culture to develop and produce the amazing increases in yield for the soil.

Experiments have shown that burying biochar in the soil can increase productivity significantly. For poor acidic soil it has sometimes been known to double or triple production! The pyrolysis process converts cellulosic matter into biooil and biochar by heating in the absence of oxygen. The biooil produced can be used like low-grade diesel fuel for heating and power generation.

The energy in the biooil produced is much greater than what is obtained by fermentation to ethanol. For example, Miscanthus, a wild grass can produce 340 GJ/hectare/year of biooil. For comparison, corn only produces 120 GJ/hectare/year (net) of ethanol by fermentation. While the corn ethanol production process emits a lot of CO2 into the atmosphere, the biochar produced as a byproduct of pyrolysis can be buried for carbon credits and crop enhancement. Every ton of biomass produces about 400 lbs of biochar by weight which is equivalent to about ½ ton of CO2. (CO2 is only 27% carbon)

Because biomass has low energy density, it is expensive to ship, pyrolysis units should therefore be close to the biomass source. Since biooil occupies about one tenth as much volume as the biomass that produced it, it can be easily shipped by tanker truck or used locally. Pyrolysis units are available that fit in a standard shipping container and can handle the needs of a small village. Using catalysts, central plants can convert the biooil and syngas to ethanol and other chemicals usually made from petroleum.

Carbon-inefficient slash and burn agriculture is practiced by 300-500 million people today. If we could convert these people to slash and char methods, we could stop the growth of greenhouse gasses in its tracks. The International Biochar Initiative and the Biochar Fund are dedicated to making that happen. This is a win-win proposition because crop yields are significantly improved while global warming is brought under control and the biooil produced provides a local source of fuel for electricity, cooking or heating. More crops, free fuel plus a revenue stream from selling carbon credits could transform these subsistence cultures while saving the planet.

As a direct result of global warming, large tracts of forests in Canada and the United States have been decimated by bark beetles. Though fast growing trees initially take in a lot of CO2 and sequester it temporarily in their wood, dead wood absorbs nothing. If we burn the trees all of the carbon they took in will be returned to the atmosphere. If termites consume the trees they will produce methane and CO2 with even worse effects. Methane is forty times worse for global warming than CO2. Pyrolysis could pay for itself by producing biooil and biochar while disposing of the dead trees to make room for healthy new ones.

The 2008 farm bill (passed over Bush’s veto!) included amazingly strong provisions for encouraging development of Biochar. The farm lobby finally got it right! Agriculture has been a big contributor to global warming and now they can be a major part of the solution. To quote James Lovelock, creator of the Ghia theory: “The biosphere pumps out 550 gigatonnes of carbon yearly; we put in only 30 gigatonnes. Ninety-nine per cent of the carbon that is fixed by plants is released back into the atmosphere within a year or so by consumers like bacteria, nematodes and worms. What we can do is cheat those consumers by getting farmers to burn their crop waste at very low oxygen levels to turn it into charcoal, which the farmer then ploughs into the field”

Farming practices turn out to be an extremely sensitive pressure point for fighting greenhouse gas. Fertilization emits oxides of nitrogen which are 140 times worse than CO2. Tilling of the soil lets carbon escape as CO2. Since agriculture began, about 140 billion tons of CO2 have been lost to the atmosphere. Carbon trading provides a financial incentive for improved agricultural practices. By growing our fuel using no till, no fertilizer crops such as elephant grass, the farmer can help save the planet, improve yields and make good money too.

Source: http://www.clrlight.org/biochar.htm

agrichar, biochar, terra preta, amazon, soil, pyrolysis, charcoal, sequestration, biomass

Last updated 363 days ago by EV World Editor