Cutting Carbon in California

Carbon capture and sequestration technologies will play an essential role in climate change mitigation, so it is not surprising that California’s plan for achieving negative emissions, described by Roger D. Aines and George Peridas in “Getting to Zero—and Beyond” (Issues, Spring 2020), hinges on their successful deployment. One important part of the plan calls for capturing and sequestering carbon dioxide from bioenergy facilities that convert biomass into fuel or electricity.

Computer models that assess decarbonization scenarios adore systems that combine bioenergy with carbon capture and sequestration (Aines and Peridas refer to this suite of technologies, known as BECCS, as “the first energy system ever invented by a computer”). But doubts about BECCS’ commercial and environmental viability persist, largely because the technology faces many of the same complications and uncertainties that plague conventional bioenergy. In theory, processes that turn biomass into energy products can have a range of positive and negative impacts on climate. The climate benefits typically decrease as production scales up, because additional demand for biomass encourages landowners to convert natural ecosystems into plantations, often in ways that transfer terrestrial carbon to the atmosphere. In practice, very few commercial bioenergy projects deliver significant climate benefits.

Aines and Peridas correctly identify “waste biomass that can be responsibly and realistically sourced without violating ecological, environmental, logistical, and economic constraints” as the most appropriate feedstock for BECCS systems, but acquiring that biomass in massive quantities is a tall order. Sourcing significant amounts of appropriate waste biomass is not something the biomass industry is currently doing or knows how to do. Selecting, aggregating, and transporting waste biomass present a complex and expensive set of problems, and to date the biomass industry has spent more time denying those problems than addressing them. As a result, much of the biomass that is now sold as “waste” to energy producers comes from live trees that were actively absorbing carbon from the atmosphere prior to being harvested.

Lots of work needs to be done to resolve, if possible, these supply chain challenges before BECCS can be scaled up in a meaningful way. The Clean Air Task Force, a group of climate and energy experts, is working with policy-makers and other stakeholders to ensure that bioenergy-related carbon fluxes are accounted for in a scientifically rigorous manner, so that biomass harvesting targets the most climate-beneficial feedstocks.

In the meantime, there are hundreds of natural gas-fired power plants in the United States that need carbon dioxide emissions controls. They offer ample opportunity to deploy and refine carbon capture technologies, to build the connective infrastructure for transporting carbon dioxide, and to develop and improve injection and geologic storage capability. BECCS systems can eventually take advantage of this downstream carbon dioxide management network, provided that careful research and testing indicates that the supply-side challenges posed by BECCS can be overcome.

Jonathan Lewis

Mapping more detailed pathways that states and nations can use to help achieve global net-zero greenhouse gas emissions is critical. Roger Aines and George Peridas are to be congratulated for taking on the challenge and dreaming big.

But ambitious dreams can be dangerous too. There is an inevitable tension between describing the possibilities and the uncertainties. Some hype is needed to win political attention and funding for essential carbon removal. But too much hype may actually undermine efforts to reduce emissions from other important sources, including some that pose hard technological challenges.

And there is hype here, most clearly in the case of bioenergy with carbon capture and storage (BECCS), presented as if it were in Schrodinger’s box, simultaneously “available and ready to be scaled up” yet “nearly imaginary.” There are indeed some forms of BECCS in use—for example, in ethanol fermentation—but these don’t actually remove net carbon, while the forms proposed by Aines and Peridas remain untested and unproven, technically and commercially.

The environmental costs of locking in continued generation of biomass wastes for BECCS use, or the ongoing removal of biomass for fire management, must also be examined more carefully. Moreover, such models may not be transferable to other jurisdictions (especially given the widely varying availability and public acceptability of geologic carbon dioxide storage).

Yet carbon removal will be needed—as well as dramatically accelerated emissions reduction. To contribute fairly to climate justice, rich jurisdictions such as California need to achieve net-zero much sooner, and will need to go beyond even that goal, to be net-negative. So a program such as this one must recognize the risks of mitigation deterrence, and build in measures from the start to minimize the risk and ensure that both carbon removal and emissions reduction can be delivered.

This will mean, for instance, devising effective separate funding, not relying on offsets. And it will demand clear separate targets for maximizing emissions cuts in the short term. Then perhaps California’s carbon dreams can become reality.

Duncan McLaren