Carbon negative - removing CO₂ from the atmosphere

Carbon-negative Bio-CCS can provide a crucial contribution to avoid dangerous climate change. Technological as well as socio-economic barriers must be taken into account when discussing where the available sustainably produced biomass should be used to attain the greatest effect in terms of fossil fuel replacement and GHG emission reductions.

As stated above, there is a broad set of technology options available through which carbon-negative value chains can be achieved, implying that the potential for negative emissions – even considering constraints such as storage availability and proximity – is significant. This is also shown in several recent reports. However, any carbon-negative scenario is based on the assumption that there is enough supply of biomass available to replace fossil fuels in each case. Moreover, it leans on the second assumption of biomass as a CO₂-neutral resource, binding up the same amount of CO₂ when growing as it emits when converted (to e.g. electricity or heat).

As it seems clear that there is not, and is unlikely to be sufficient amounts of biomass available to cover a fossil fuel replacement in all abovementioned sectors, particular attention must be given to sectors for which no alternative GHG reduction tools are available, such as biofuels production for aviation and heavy transport. While the theoretical potential for negative CO₂ emissions appears to be huge, the existing global supply of sustainably produced biomass imposes severe limitations on this potential. In August 2011, the IEA GHG and Dutch energy consultancy Ecofys published their joint report “Global Potential for Biomass and CCS”. Findings in this study imply that the projected realisable negative emissions potential in 2050 amounts to 3.5 gigatonnes annually. If sustainable biomass supply could be increased however, the annual potential for CO₂ removal from the atmosphere could increase threefold or more. This implies that innovative and sustainable ways to massively increase that supply of biomass will be key elements to enable the full potential for reductions in GHG emissions on the scale that the IPCC states is required.

To avoid negative direct and indirect land use change impacts from biomass production, biomass feedstock which does not compete with land used for food or other purposes needs to be developed. Developing micro- and macro-algae production as well as saltwater plants as novel biomass feedstocks might be one such option. Such saltwater based biomass feedstock supply is a less explored possibility for large scale biomass feedstock production. Projections of the theoretical amounts that can be produced of such biomass are needed to give an idea of its potential contribution to carbon-negative value chains.

Bio-CCS is the synergy of two GHG reduction methods: CCS, and extensive use of biofuels/bioenergy. While both are acknowledged as necessary in most high GHG reduction scenarios, in many settings both are perceived by the general public as controversial. This controversy seems likely to present a significant hurdle to the widespread deployment for each of the two. The promising potential of their combination could however reinforce both in terms of public acceptance.

The debate on EU biofuels policy has been raging fiercely in the last few years. In the first half of 2008, (1^st generation) biofuels sustainability came under heavy fire in the context of the European Union energy and climate package, initially presented by the European Commission in January that year. Increasing the level of biofuels in the EU transport sector to 10 % by 2020 was seen as a way to reduce the sector’s steadily increasing carbon footprint, but fears that direct and indirect land-use changes caused by increased biomass production will lead to e.g. soaring global food prices and deforestation turned into a sustainability debate which still is strongly present today. While the European Commission and others are working on methodologies to secure biofuels sustainability, the biofuels industry is arguing that any biomass sustainability criteria imposed must also be valid for other biomass utilisation. With an expected increase in co-firing biomass in power plants, it is likely that a similar debate will surface – this was also shown by the Commission’s 2010 consultation on (possible) sustainability criteria for solid and gaseous biomass.

All in all, relevant policies must be identified. 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.