Tuesday, February 18, 2014

BERCShop: Closing the Carbon Cycle

SF cloudPhoto credit: angeloangelo / Foter / CC BY

As Noah Deich discusses in this VEC Guest Blog – today, February 18th, 2014, BERC will host a BERCshop on the topic of: Closing the Carbon Cycle – Scaling Up Carbon Removal Solutions (Registration page).

So what exactly is the notion of removing greenhouse gases from the atmosphere?

Since the dawn of the industrial revolution, people have found immense value in inventions (like cars, power plants, and factories) that release carbon dioxide (CO2) and other greenhouse gasses (GHGs) into the atmosphere as byproducts. The same, however, cannot be said for inventions that remove GHGs from the atmosphere. As a result, humans activity today generates approximately 50 more gigatonnes (Gt = 1 billion metric tons) of GHG emissions annually than it did centuries ago.

“to limit warming to 1.5o C, we will have to stop emitting GHGs entirely by 2050 and generate average CDR levels of 5 Gt annually from 2050 to 2100″

Complicating matters, the earth has absorbed only a fraction of the roughly 1,000 Gt of cumulative anthropogenic GHG emissions, leaving atmospheric concentrations of GHGs nearly 40% above pre-industrial levels, and ocean acidity levels about 30% higher. Left to its own devices, the earth will take millennia to draw down remaining anthropogenic GHG emissions. This is bad news for our planet: the dramatic changes to earth’s climate and ecosystems that result from elevated atmospheric GHG levels are here to stay unless humans start removing GHGs from the atmosphere.

Source: Figure 7.3 of 2007 IPCC Climate Change Report (Note: 1 GtC = approximately 3.7 Gt CO2)

Enter: CDR.

CDR is equivalent to generating “negative GHG emissions.” That is, a CDR solution:

1. Captures more CO2 (and/or other GHGs) from the atmosphere than it releases, and

2. Prevents that carbon from returning to the atmosphere for long periods of time.

On what scale is CDR needed to prevent climate change?

The 2013 UN Emissions Gap Report estimates that, to limit warming to 1.5o C, we will have to stop emitting GHGs entirely by 2050 and generate average CDR levels of 5 Gt annually from 2050 to 2100.* At a cost of $100 to remove and store a ton of CO2 from the atmosphere, this figure translates into an annual cost of $500 billion for CDR. For comparison, Gross World Product stands at roughly $70 trillion today.

The UN Report proposes a very aggressive GHG-emission reduction timeframe: if GHG-emitting technologies are phased out more slowly than the UN report projects, then required CDR efforts could balloon considerably.

What are the different main approaches currently being considered for CDR?

The four primary approaches to CDR include: 1) biomass storage, 2) air capture, 3) geologic sequestration, and 4) marine sequestration.

1)     Biomass storage:

 The planet has been drawing down hundreds of Gt of carbon from the atmosphere annually for billions of years through photosynthesis: every growing season, plants transform atmospheric CO2 into biomass. After each growing season, however, the earth releases a roughly equal quantity of carbon from plants back into the atmosphere (through decomposing biomass).

Through a variety of mechanisms, CDR practitioners hope to tip the balance of this natural carbon cycle so that less carbon gets stored in the atmosphere. For example, afforestation (planting new forests) and grassland management techniques aim to increase the overall quantity of biomass in the ecosystem. Increasing the amount of carbon trapped in plants, the theory goes, decreases the amount of carbon in the atmosphere.

Other biomass storage CDR approaches seek to alter the carbon cycle by preventing (or significantly increasing the time it takes) carbon trapped in biomass from emitting back into the atmosphere through its natural cycle. One such approach is biochar (charcoal), which is created when organic matter is pyrolyzed (burned without oxygen). Biochar can potentially remain in solid form for hundreds of years without decomposing – so if biochar a) is produced from feedstock that grows back annually, and b) is reapplied to the soil after production, then it has the potential to transfer significant quantities of carbon out of the atmosphere.

Based on a similar idea to biochar, biomass energy with carbon capture and sequestration (BECCS), offers the potential to sequester large amounts of carbon dioxide in the earth’s crust. When biomass power plants burn sustainably grown feedstocks to produce electricity, the resulting process is carbon neutral, as any emissions from burning the biomass are removed the following year when the feedstock grows back. However, if such power plants install technology to isolate CO2 from the plants’ emissions, this CO2 can be injected into impermeable rock formations deep underground, in effect transferring CO2 from the atmosphere to the earth’s crust.

2)     Air capture:

Direct Air Capture (DAC) devices operate analogously to “artificial trees.” Such DAC devices isolate CO2 from the air using chemical processes, in the same way that plants do through photosynthesis. Storing the resulting CO2 in impermeable rock formations in the same way as BECCS (or otherwise preventing the CO2 from returning to the atmosphere) promises significant CDR potential.

3)     Geologic sequestration:

Transferring carbon from the atmosphere into rocks is another option for CDR. Some minerals, such as olivine, precipitate CO2 from the atmosphere when exposed to air. The resulting carbonates from this reaction have the potential to sequester the formerly-atmospheric carbon in stable rock formations. Mining large quantities of olivine and exposing it to open air could result in the sequestration of large amounts of atmospheric CO2.

4)     Marine sequestration:

Marine sequestration, a more controversial category of CDR approaches, attempts to reduce atmospheric CO2 concentrations by altering the oceans’ natural carbon cycles. Fertilizing the ocean with iron to stimulate phytoplankton blooms, for example, has been proposed as a means to transfer carbon from the atmosphere to the depths of the ocean, where the carbon would remain for millennia. The theory goes that phytoplankton blooms would store carbon in both the plankton and other organisms further up the food chain that flourish because of a plankton bloom. When these organisms die, they (and the carbon they removed from the air and stored in their bodies) would slowly sink to the ocean depths. Whether this theory actually results in significant CDR in practice, however, remains highly uncertain given the current lack of research on this topic.

The science stands even more equivocal on the related CDR technique of shellfish sequestration, as best illustrated by this wonderful paper, whose author simultaneously argues that increasing mollusk farming by a factor of 10,000 could either reverse humankind’s entire contribution to climate change within a century… or exacerbate climate change dramatically, depending on whether one trusts the arguments in the body of the paper or those in its footnotes.

Some have proposed a hybrid biomass/marine sequestration CDR approach: dumping crop residues in the deep ocean could prevent this organic matter from decaying and releasing carbon back into the atmosphere for millennia.

What criteria can we use to evaluate the various approaches to CDR?

1)     Overall storage potential. If we need to remove and store hundreds of Gt of CO2, it is important that the CDR solutions we pursue can sequester a similar magnitude of CO2. To date, many parties have attempted to assess the potential for different approaches to CDR (biological, underground storage, for example).

2)     Technology maturity and complexity. All CDR technologies currently lie at the very beginning of the technology adoption curve. Investing in the R&D and marketing to create cost-effective CDR techniques will take significant time and financial and human resources – therefore less technologically and/or conceptually complex CDR solutions would presents significant benefits.

3)     End market for stored carbon. As noted above, atmospheric carbon can be transformed into a variety of end products, and figuring out how to make money by utilizing these different end products will likely prove critical for the near-term viability of many CDR technologies. Biochar, for example, offers potentially significant agricultural and wastewater treatment co-benefits, and currently generates millions of dollars of sales annually for such uses (not quite the trillion-dollar electricity or transportation industries, but definitely a start). The greater the potential for selling the byproducts of a CDR technique, the greater the chance that it will flourish.

4)     Risks of unintended consequences of large scale adoption. As with any large-scale interference of a complex geosystem, unintended consequences present enormous risks. The CDR approaches that conceptually present the lowest risk for such unintended consequences will likely have an easier time winning initial support.


BERCshop: Closing the Carbon Cycle – Scaling Up Carbon Removal Solutions

February 18th, 6-8 PM (networking reception to follow), UC Berkeley Boalt School of Law, Room 295

Register and more details at: 

Come learn about the “carbon negative” industry at the first BERCshop of 2014! A renowned group of academics and business leaders will share their thoughts on emerging technologies, business models, and the actions required to deploy carbon negative solutions at the scale needed to avert climate change. Ken Caldeira from the Department of Global Ecology at Stanford University will deliver the key note address, followed by Jane Long from UC Berkeley moderating a panel discussion featuring:

This workshop is hosted by the Berkeley Energy & Resources Collaborative and sponsored by the Virgin Earth Challenge.