Mar 30, 2012

A carbon-negative economy: A practical prospect or a pipe dream? |

By Marc Gunther
Published March 29, 2012

“Let’s not simply reduce the CO2 emissions going up into the atmosphere. Let’s draw them down.”

So says Robert Brown, a professor of engineering at Iowa State University and a leader of the university’s Initiative for a Carbon Negative Economy and its Bioeconomy Institute. Those are interdisciplinary campus efforts to develop ways to remove carbon dioxide from the atmosphere by growing plants or algae, making them into fuels and burying their carbon residues in soil -- and make money doing it.

The notion that we can generate wealth and remove CO2 from the air is obviously appealing. As atmospheric concentrations of CO2 rise and climate risks grow, so does the need for carbon-negative technologies that pull CO2 from the air, as plants do, and then store it underground or deep in the ocean.

But is this practical or a pipe dream? That’s what Brown and his colleagues at Iowa State and its Bioeconomy Institute want to find out, as they explained this week at a two-day workshop on biochar -- that’s the term used for the charcoal created when biomass is decomposed at high heat, in a process calledpyrolysis. The workshop was part of the Carbon War Room‘s Creating Climate Wealth Summit in Washington, D.C..

The Carbon War Room, as you may know, is a nonprofit created by Richard Branson of Virgin fame to unlock gigaton-scale, market-driven solutions to climate change. Its new president will be Jose Maria Figueres, the former president of Costa Rica. The group is also tackling projects around energy efficiency, renewable jet fuel, low-carbon ocean shipping and sustainable livestock.

Biochar has been around for a long time, but it’s getting new attention from government and business. The Iowa State researchers last fall were awarded a $25 million research grant from USDA to see if they can find ways to use marginal farmlands to grow perennial grasses and turn them into biofuels and biochar. Local firms like ADM, the agribusiness giant, have expressed support.

This week’s biochar workshop attracted an interesting crowd. USDA was there, as were executives from Conoco Phillips (they are interested in biofuels), Tenaska Energy (also biofuels), Phycal (which makes fuels from cassava and algae), Cool Planet Biofuels (a California startup funded by Google that is working on negative-carbon fuels, using miscanthus, among other feedstocks) and Biochar Solutions (which makes machinery to make biochar.) It’s very, very small but a biochar industry seems to be taking root.

Biochar 101

Biochar, as I wrote last summer, can be traced back to Brazil, where dark soils in the Amazon region are known as “Terra Preta.” Some scientists believe they were created as long as 4,500 years ago, and that they helped support a complex, farm-based civilization in the Amazon, despite the region’s poor soil.

Biochar isn’t just one thing, as Brown explained. It can be made using different processes from cellulosic feedstocks including wood chips, switch grass or corn stover, or from lipid-rich biomass such as rapeseed, soybeans or micro-algae. Essentially, through, the idea is to speed up and optimize the natural process in which plants (carbohydrates) decompose into fuels (hydrocarbons).

Here’s how the Carbon War Room explains it:

High-yielding varieties of terrestrial plants or aquatic species are used to fix carbon in the form of biomass. The biomass is collected and through an oxygen-starved process known as pyrolysis, is converted to an energy-rich liquid called bio-oil and a carbon-rich solid called biochar.

The bio-oil is upgraded to transportation fuels or used to generate electric power, thus providing high-value products to the economy. The biochar is incorporated into farmland where it serves the triple purposes of sequestering carbon from the atmosphere for millenia, building soil carbon and recycling nutrients removed with harvested biomass.

Iowa State has a small processing unit that can process about 1/4 ton per day of biomass, Brown told me. The researchers are feeding it switchgrass, wood chips and corn stover (the non-edible parts of corn plants, which, needless to say, are plentiful in Iowa.)

Many obstacles remain to taking biochar to scale as a climate solution. For one thing, Iowa farmers aren’t particularly interested in biochar, at least not in paying for it -- perhaps because their soils are among the richest in the world. The agricultural benefits of biochar -- its ability to retain water or nutrients -- remain largely unproven.

David Laird, an Iowa State soil scientist who is working on the project, said that in a dry year, soil enriched with biochar “could have a significant positive impact on crop yields” by retaining water. “But in a wet year, that’s meaningless,” he noted. Biochar would probably have a far greater value if it could be used to enrich poor quality soil, where it could not only increase crop yields but drive up land values. In Africa, for instance, some people say biochar could have a big impact on agriculture.

The USDA grant and other funding will enable the Iowa State team to better understand both the science and economics of biochar and biofuels. They’ll have to wrestle with some tradeoffs: So-called fast pyrolysis processes biomass at high heat, which makes more fuel and less biochar; that’s good for the business model, not so good for climate impact. By contrast, slow pyrolysis generates more biochar to sequester but less fuel to take to market.

Meanwhile, Brown and Laird are experimenting with biochar in their own backyards. Brown says he grew six-foot-tall pepper plants, and Laird has been growing tomato plants.

How are the tomatoes doing, I asked him.”They’re great,” he replied. “But it has nothing to do with me, and a lot to do with my wife.”

No comments: