Carbon negative

Carbon negative - removing CO2 from the atmosphere. A possible future solution to combat global warming and ensure sustainable power production can be large power plants fuelled by algea combined with CCS. Algea grows faster than any other plant, and as it grows it consumes CO2. When the algae is combusted in a power plant with CCS, the CO2 consumed from the atmosphere will end up stored underground.

Technology and policy breefing:
Biomass with CCS – enabling a carbon negative energy system
Carbon capture and storage (CCS) is the new tool for combating global warming that we didn’t have in Kyoto in 1997. Across the world, business, politicians, researchers, NGOs and the public are realizing that CCS can be instrumental in realizing the serious cuts in greenhouse gas (GHG) emissions that we need to avoid dangerous global warming. The same can be said of renewable energies. Solar and wind energy have enjoyed unrivalled growth rates in the last decades, and biomass and waste resources are increasingly being used for energy applications. But the latest research on climate sensitivity and mitigation scenarios show that this is not enough; reaching the 2 degree Celsius target is probably not achievable without combining bioenergy with CCS to produce carbon negative energy.

Reaching the 2C target means stabilising at less than 450 ppm CO2-eq
The EU and several other countries have vowed to limit the average temperature increase above pre-industrial levels to maximum 2 degrees Celsius, with better than an even chance. This is deemed necessary to avoiding passing dangerous tipping points beyond which climate change is likely to accelerate. As Figure 1 shows, this means that the atmospheric concentration of greenhouse gases must be stabilised at less than 450 ppm-eq (the blue line shows the 50 percent percentile). Consider now that the current concentration level is about 430 ppm CO2-eq.

Low-stabilisation scenarios rely on biomass with CCS
Various scenarios have been produced to show how a portfolio of existing and new climate solutions can be put together to achieve deep cuts in greenhouse gas emissions. The latest study is a comprehensive modeling effort undertaken by the EU-funded ADAM project. One important finding here is that the more ambitious the emission reduction target, the more important becomes a large-scale implementation of biomass with CCS (Knopf, et al. 2008). This corresponds well with other findings, such as Bellona’s How to combat global warming? (2008), which found that the energy sector has to go carbon negative by means of biomass and CCS to offset hard-to-handle emissions in other sectors.
The assumption in the mentioned scenarios is that the world achieves an almost immediate stabilisation of emissions and sharp cuts already by 2020. Recent observations suggest that these assumptions may be overly optimistic. Political observers would note that the world is still far from seeing the adoption and enforcement of the policies necessary to achieve a peak in emissions anytime soon. Climatologists are observing that climate change already is having stronger impacts on the world’s ecosystems than suggested by the most updated climate models. This apparently is not unexpected by the IPCC in its 4th assessment report: Since carbon feedback cycles are not properly accounted for in climate models, “the emission reductions to meet a particular stabilization level […] might be underestimated” (IPCC 2007). This underscores the importance of developing carbon negative strategies.

The enabling technology already exists or is being developed
Large-scale implementation of biomass with CCS is technically speaking a straight-forward concept. The first step is replacing fossil feedstocks with biomass in large-scale plants, such as power plants or factories. This is already happening on industrial scale, either through co-firing biomass with coal or by using solely biomass. Vattenfall, for example, is investing in a program to co-fire three power plants in Denmark. The plan is to replace 0.75 million tons of coal with 1.2 million tons of biomass by 2013. Similarly, Drax has announced plans to build three dedicated, 300MW biomass power plants and a 400 MW biomass co-firing plant in the UK. Biomass is also used to replace fossil feedstocks in process industry, such as cement factories and steel mills.
The second step is to add CCS technology to the facility. Vattenfall’s first commercial-scale CCS demonstration plant is being built at Nordjyllandsværket in Denmark. This is one of the plants which Vattenfall plans to cofire with 30 percent biomass. Because part of the stored carbon dioxide was absorbed from the atmosphere by the biomass as it grew, this achieves a net negative emission, removing 0.5 million tons of CO2 from the atmosphere per year, see Figure 2.
The energy/mass ratio is lower for biomass than for coal, and dedicated biomass plants have significantly lower efficiencies than coal power plants. Cofiring biomass in coal power increases the efficiency of using biomass for energy, and could make less energy-rich types of biomass such as seaweed suitable for combustion.

Ensuring sufficient supply of sustainably produced biomass is critical
Biomass currently accounts for about 10 percent of world primary energy use, two thirds of which is used for small-scale cooking and heating in developing countries. In industrialized countries, biomass is used for heat in industry and residences, transport fuels and electricity generation.
Biomass production is subject to a range of sustainability constraints, such as: scarcity of arable land and fresh water, loss of biodiversity, competition with food production, deforestation, and scarcity of phosphorous. It is important to make sure that biomass is used in a way that maximizes both energy and climate benefits. On these terms, carbon-negative energy applications can be expected to fare well.
Large-scale deployment of biomass with CCS requires that we ensure sufficient, sustainable supply. New concepts, such as producing aquatic microalgae on lands not suited for food production and macro algae in the sea, promise a solution to this problem. These species grow well in salty, waste or brackish water, and large-scale and small-scale, high-tech and low-tech production technologies exist.
Several power plants, both in the US, Germany, India and other countries, have been or are planned to be fitted with micro algae production facilities, in which the algae recover about half of the CO2 in the flue gas. While the remaining CO2 could be covered and geo-sequestered through gas separation processes, the algae produced from flue gas can be recycled back into the power plant, co-firing it with other (fossil or biogenic) fuels.

Policy and accounting practices needs to accommodate carbon negative CCS
Acknowledging that the climate does not care where the CO2 comes from allows us to rediscover a substantial potential for reducing emissions of CO2. Sweden is a case-in-point. The CO2 emissions formally reported to the UNFCCC amounts to about 67 million tonnes per year. So when Sweden is to fulfil its ambition to become ‘carbon-neutral’ by 2030, this means cutting the emission of fossil CO2 by 67 million tonnes. Reaching this target will not only be easier when the 23 million tons of biogenic CO2 currently emitted from large pulp-and-paper plants are included; fitting these plants with CCS would even allow a ‘carbon-negative’ Sweden. Now that would send a message.
Current policies for promoting the use of bioenergy are mostly aimed at substituting fossil energy with bioenergy, most notably so in the housing and transportation sectors, where the production and use of biofuels is mandated and/or subsidized. This creates a disincentive to use biomass for bioenergy with CCS applications, even if this would be more effective and efficient, both in terms of resource/energy and climate protection. Current emission trading schemes also give no incentive to capture (reduce) biogenic CO2 emissions. Policy frameworks must therefore be updated. This is particularly urgent in the context of the UNFCCC negotiations ultimo 2009.

Biomass with CCS can enable the large-scale creation of jobs in devloping countries
Biomass with CCS – the carbon negative strategy, offers an opportunity to create a global green energy commodity market that offers poorer countries a chance to ensure economic development while at the same time committing to an ambitious deal in Copenhagen. Labour-intensive biomass production could be established to supply large amounts of biomass to a growing international market for biomass. This gives developing countries an incentive to accept a stringent target for emission reductions in 2050, as it means that the need for biomass with CCS increases.

References
Bellona. How to combat global warming. Oslo: The Bellona Foundation, 2008.
IEA. Energy Technology Perspectives 2008. Paris: International Energy Agency, 2008.
IPCC. Climate Change 2007: Synthesis report. Geneva: Intergovernmental Panel on Climate Change, 2007.
IPCC. Climate Change 2007: The Physical Science Basis - Summary for Policymakers - Contribution of Working Group I to the Fourth Assessment Report of the. Geneve: INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE, 2007.
Knopf, Brigitte, et al. D-M2.6: Report on first assessment of low stabilisation scenarios. Project deliverable: Adaptation and Mitigation Strategies: Supporting European Climate Policy, Potsdam Institute for Climate Impact Research (PIK), 2008.
 

See also:

• How to combat global warming