Expert Q&A: Negative Emissions & Environmental Assessment Could Help Save the Planet

by Anthony J. Campanella (State University College at Buffalo/Planet Forward) George Washington University recently hosted a daylong workshop for NGOs on carbon dioxide removal and negative emissions. ... One of the experts presenting at the event, Stanford University senior research scientist Katherine Mach, sat down with us to tell us more about herself and the technology. Here's what she had to say:

PF: Can you briefly describe the three different approaches to negative emissions and tell us which approach you think is most likely to be implemented on a mass scale?

Mach: So I think of the spectrum of carbon-dioxide removal as having two poles. On one pole we have biology and on the other we have engineering. I’m going to describe three [categories], one at the end of each of these poles and one that lies in the middle. The first [category] are approaches that are tightly linked to stewardship. So if we better manage our forests, they can hold more carbon. If we better manage our agricultural fields, the soils can take in more carbon. We know how to do these types of approaches and in some cases know how to do them really well. For example, California’s Forest Offset Program is the first legally enforceable program in forest offsets. It’s happening at 5 million tons per year at a relatively cheap cost of $10 a ton. The second [category] is still biologically based in terms of how carbon is taken out of the atmosphere but it’s more engineered. This could be anything from bio-char, to building with biomass, or bioenergy paired with carbon capture and storage (BECCS). These are approaches that are more expensive, not quite ready but could in many cases play an increasing role depending how in particular we decide to value the role of carbon in that equation. The third category [that includes] direct air capture, is a fully engineered approach. With this approach you are using carbon capture and storage to get carbon into geological formations underground. Looking across this spectrum of approaches, we have an order of magnitude differences in current cost: about $10, $100, $1000 per ton [respectively]. We are looking at different levels of engineering complexity, different spatial footprints for each approach. Direct air capture might make a whole lot of sense once we have abundant clean energy but until we have a lot of energy to put into the “capture” part of the equation it’s hard to imagine bringing it rapidly to scale. I see all of these [approaches] providing a lot of different opportunities for industries at the millions and to many millions tons scale. The real question moving forward is which ones, if any, can we get to the billion tons scale.

PF: How far out are we from developing these technologies and utilizing them? How many years of development do we need in order to utilize these technologies in a way that is fully beneficial?

Mach: For that first category we know how to do a lot of that now. Managing forests well, utilizing cover crops or compost additions in agricultural management are things that are available now. So the question is how do we create a financial signal – either through conservation or climate policy to make it a reality. In the BECCS space [second category] we see a number of plants at demonstration scale, about 1 million tons per year, we are starting to figure out how to make this happen. Some of our work at Stanford has tried to look at near-term, low cost, and commercially available opportunities in that space. For example, bio refineries that are working on a yearly basis to produce ethanol are a low cost option in capturing CO2. Direct air capture [third category], we are also starting to see prototype scale projects. For example there is a company now in Switzerland that is using direct air capture to filter CO2 into greenhouse agriculture as a way to get plants to grow faster. It’s hard to say exactly how long the [timeframe] is, recognizing for direct air capture you need a lot of energy to make it happen and across that spectrum you need some way to price carbon so we can make these policies translate into reality. READ MORE