Biochar: A better backup for solar/wind?
By RON LARSON
Biochar, a new form of biomass, deserves some consideration as a backup for inherently intermittent wind and solar. In fact, it may be necessary if we are ever to achieve the carbon-neutral world called for by climate change scientist James Hansen.
From a carbon dioxide (CO2) emissions standpoint, natural gas is an improvement over coal — but, to achieve 350 parts-per-million CO2, it too must be replaced. I am a believer that a solar-wind-biomass hybrid approach will give the world its best shot at achieving fossil fuel-free electric generation. And I’m convinced the best biomass option, due to its carbon-negativity, is biochar.
Since it’s a nascent, under-the-radar technology, let me give you a quick introduction.
Biochar is ordinary charcoal finely ground, and placed in soil. The charcoal comes from biomass — say switch grass or some forest or agricultural byproduct, for instance — that is thermochemically decomposed in anoxic environments at high temperatures. The soil deposition is what makes it carbon-negative; it effectively sequesters biomass’ CO2 underground, instead of allowing it to reenter the atmosphere. Biochar can tie into electricity production, as one of its byproducts, pyrolysis gas, is highly combustible. Another method of production uses hydrothermal carbonization, which produces a “waste” product that is 450°F (230°C) and can be used to turn a turbine. (For further details about production techniques, lifetime, soil benefits, etc., see biochar-international.org/technology.)
Biochar is moving along technology-wise, but has some pitfalls that have thwarted development. In effect, there are only a handful of small-scale projects in operation today — including in Japan, the United Kingdom, Australia and the United States. Constraining factors include a lack of research and incentive funding, no mass-produced conversion technologies and imperfect understandings of soil science. Biochar R&D is hurt locally by the United States’ lack of recognition of climate change — since one of its primary benefits (and my priority) is carbon-negativity.
But biochar’s benefits are many, and its potential is far-reaching. By reducing the need for fertilizer and irrigation and increasing nutrient retention, biochar boosts soil health. It also captures nitrous oxide and methane, both of which are potent greenhouse gases. This gives biochar enormous potential as a greenhouse gas-offsetting agent — by my measure, its impact could be every bit as large as today’s total fossil fuel contribution.
With the right strategies, it will be possible to build biomass/biochar’s infrastructure to this level. In places, biochar could fit seamlessly into the utility grid. It lends itself particularly well to mid-sized (10- to 20-megawatt), community-based combined heat-and-power biomass facilities. Unlike wind turbines and solar arrays, these facilities come with an on-off switch. That’s precisely my selling point for biochar — it’s a renewable that can come on when you need it to.
While the U.S. electric grid is still less than 3 percent dependent on intermittent wind and solar, both industries have positioned themselves well for exponential growth. In lieu of relying on natural gas, a peaking source, renew- able energy proponents have touted grid-stabilizing tools such as battery backup, pumped hydro and compressed air. I strongly encourage them to start paying attention to carbon-negativity and especially to the technology I think will be least costly: biochar.
Ron Larson formerly served as chair of the board of directors for the American Solar Energy Society (2006 to 2007) and is an ASES fellow and life member. In retirement, he comfortably resides in the University of Colorado’s 2002 Solar Decathlon home.