Burning Fuel Into Fertilizer: Gasification and Biochar0

Jeremy Faludi | Wed Sep 7 2011

What if burning a fuel could actually be good for the planet? It may sound crazy, but when done right, gasification—the extraction of fuel gases from organic matter—combined with biochar production can sequester more carbon than it emits, making it a carbon-negative fuel.

The process works by taking agricultural or forest waste and pyrolizing it (similar to burning, but without the oxygen). This breaks down complex organic molecules into hydrogen gas, carbon monoxide and other burnable gases, as well as tars and non-useful gases like CO2.

Burning these gases as fuel, of course, does cause greenhouse emissions, but less is emitted than if the agro-waste were burned in the open air or dumped with the resulting methane emissions from decomposition. Although much biomass waste is already used as compost or in production, in the U.S. alone over 300 gigatons of biomass per year are simply disposed of according to Danny Day, founder of the gasification startup Eprida.

Sunny and Char

But gasification is only half the story. The special charcoal left over as a byproduct (“biochar”) is an excellent fertilizer; this is where the carbon sequestration comes in. With the ability to triple farm yields, biochar is thought to be the secret of the fertility of Brazilian terra preta soils.

The biochar locks carbon in soil and plants in a more reliable, natural, and long-term stable way than traditional methods. It also helps soil uptake and retain fertilizers and causes “a five to 10 fold reduction in nitrous oxide emissions,” according to some soil scientists. This is an important fact considering that worldwide nitrogen oxide emissions from soil are estimated to be a bigger greenhouse source than the steel industry or the entire chemical industry.

With the ability to triple farm yields, biochar is thought to be the secret of the fertility of Brazilian terra preta soils.

Not all gasification sequesters carbon. The coal industry gasifies coal to create synthetic natural gas (“syngas”) for chemical feedstocks, but the National Academy of Sciences says that using it for fuel would cause about double the CO2 emissions from oil. It’s the gasification of farm and forest waste that abates carbon, and the use of biochar as soil enrichment that sequesters carbon.

Large-scale impact

Danny Day of Eprida calculates that while burning gasoline emits about 60 kg of CO2 per gigajoule of energy (about 6 gallons of gas), some methods of gasification and biochar can sequester over 100 kg of CO2 per gigajoule of energy generated.

How much could this help climate change globally? Eprida estimates that biochar-fertilizing an area roughly three times the size of Texas could absorb 1.9 gigatons of CO2 per year—almost a third of the emissions from global human energy use. That makes it potentially a huge contender compared to other sequestration schemes.

The players

People have been using gasification for over 200 years, though its possible climate change benefits were only discovered in the past decade or so. In World War II Europe, over a million vehicles ran on wood gasifiers, due to gasoline rationing.

Today, a small but growing number of companies and researchers are working to make gasification a viable clean energy source. They range from small startups like All Power Labs and Eprida—sometimes working with national laboratories like NREL and ORNL—to industrial-scale companies like Chinook Energy, who started as a metals recycler and are now gasifying municipal waste to simultaneously recover metals and generate energy.

Fertilizing an area roughly three times the size of Texas could absorb almost a third of the emissions from global human energy use.

In addition to companies in rich Northern countries using gasification and biochar to improve energy independence and reduce climate change, there are philanthropic nonprofits like Biochar International and professor Amy Smith’s group at MIT who use it in poorer countries to improve health and reduce poverty in rural areas.

In her 2006 TED talk Smith said, “this is about the most exciting thing in my life right now,” because of the enormous difference it makes in people’s lives in Haiti and other countries.

A future of energy hackers?

Gasification is only recently emerging as a clean energy technology, though it has a long proven practical history. With more experimentation and investment, gasification and biochar could become a game-changing energy sector—one that actually remediates as it generates.