Hydrogen energy and renewable natural gas get the most attention, but the push to turn the Central Valley’s ag waste into renewable energy could also boost local production of byproduct whose local benefit remains somewhat more puzzling: biochar.
The charcoal-looking substance, created when wood is super-heated in a low-oxygen environment, has been shown in some cases to increase water retention in soil, and can be used as fuel, a water purification component or even a carbon management tool.
But as interest grows in the air-quality and tax-credit advantages of turning orchard trimmings and other local biomass into energy rather than burning it openly, doubts have been raised about biochar’s best use and, ultimately, its value on the local market.
Research has shown the material’s characteristics vary widely, depending on the source matter, and not all soil types appear to benefit noticeably from the introduction of biochar. Plus, in the absence of large-scale scientific tests in California across a span of many years, government has not come up with financial incentives encouraging its production and use.
Energy Program Chief Scientist Roger D. Aines at the Lawrence Livermore National Laboratory said it may turn out that the best use of biochar is simply to feed it back into the waste conversion process as fuel for generating the heat required.
Or it could be, he said, that it might be best to minimize production of biochar so that more byproduct carbon dioxide can be buried deep underground through injection. Federal incentives certainly make that an attractive option, he said.
“I hate to be a downer on technology,” Aines said, “but I think it’s important to recognize what it’s ready for, and biochar is ready for testing.”
Deputy Director Colin Murphy at the University of California, Davis Policy Institute for Energy, Environment and the Economy largely agreed. He said by email that optimizing the production of fuels like hydrogen during gasification or pyrolysis of biomass involves a tradeoff on biochar production, “so there’s a real question about what balance of products will yield the best economic and environmental benefits.”
Biochar is sold at local home-improvement stores for use as potting soil. Lately, a few farmer inquiries have come to The Holloway Group, a Bakersfield-based company that sells soil amendments and provides orchard removal and recycling services.
Holloway CEO Brian Maxted said by email the company is actively looking into the benefits of biochar. One option, he said, is to gather up the ground-up orchard material the company removes from clients’ farmland, then send it for processing at one of the waste-to-energy plants proposed for construction in Kern.
Maxted said the company appreciates the circular-economy and sustainability aspects biochar appears to present, but he noted a key factor will be the cost impact on farmers. He said it’s still too early to know.
“Our early opinion,” he wrote, “is that not all biochar is created equal, and, depending on how the biochar is made, and from what carbon sources, determines not only the overall agronomic benefit of an application but also the ability for the producer or user to take advantage of offsets that may be available in the future for sequestering the carbon rich resource within the soil profile.”
Biochar is planned to be a byproduct of the biomass-to-energy plant Iowa-based technology company Frontline BioEnergy proposes to build in McFarland for handling 300,000 tons per year of nut shells and other waste.
The material would be converted to 3.5 billion megajoules of energy per year in the form of methane for use as truck fuel instead of diesel. Also coming out of the process would be 400,000 tons per year of CO2 — and 12 dry tons of biochar for every 100 dry tons of biomass, or roughly 36,000 tons per year.
An assessment by the U.S. Environmental Protection Agency concluded biochar from the project has several possible applications, including as a soil amendment, kiln fuel for cement production to displace fossil fuels or feedstock for the project itself. The agency also noted the project’s biochar could serve to sequester carbon because, after being raised to very high temperatures in the fuel production process, the charred leftovers would be stable enough to last at least 1,000 years.
Whole orchard recycling, an alternative to converting biomass to energy that has gained interest locally, is seen by some as preferable to biochar production and use. The process is simpler and takes less energy to carry out: wood from aging almond orchards is cut down and shredded before being reincorporated into the soil. Studies point to increased tree growth and higher nut yields.
Soil scientist Milt McGiffen at the University of California, Riverside said by email there is value in producing biochar locally to avoid shipping charges while also improving soil. The material can help retain nutrients in soil and maybe serve as a substitute for peat moss and possibly vermiculite.
“The problem is,” McGiffen wrote, “that it is not going to double your yields, so it is hard to justify on a short-term basis.”
