Post-combustion carbon capture - negative emissions from bioenergy

Siemens and E.ON to cooperate on post-combustion carbon capture - towards negative emissions from bioenergy

Few people know that biomass power plants can be coupled to carbon capture and storage (CCS), to yield negative emissions energy - the most radical tool in the climate fight. Such 'bio-energy with carbon storage' (BECS) systems and the renewable energy crops that are used as their feedstock actively remove CO2 from the atmosphere by locking biogenic carbon dioxide up in geological formations. No other energy technology can attain this carbon-negative status. Renewables like wind, solar, hydro or geothermal, forever remain carbon-neutral at best (illustration, click to enlarge). However, for CCS to work, optimised technologies are needed that can efficiently capture the biogenic CO2 at the power plant, before it reaches the atmosphere.

Several options exist, all with their advantages and drawbacks: capturing the CO2 before the fuel is combusted, which could be applied to biohydrogen and biogas; capturing the carbon dioxide gas during a modified combustion process (oxyfuel); or capturing it after the combustion of the fuel, from the power plant's flue gases. Organisations around the world are developing such technologies, mainly for applications in coal and gas-fired power plants. But the basics remain the same for biomass (co-firing) power plants. For this reason, we actively track developments in CCS - ironically, the coal sector may be developing the very technologies needed to design the most radically green energy system imaginable.

What is more, when CCS is applied to biomass, the biggest argument leveled by environmentalists against the technology - the potential for leakage of CO2 - becomes invalid, because the stored CO2 is biogenic in nature and does not come from fossil fuels.

Scientists from the Abrupt Climate Change Strategy Group have found that if we apply BECS systems on a global scale, we can cool the planet and go back to pre-industrial CO2 levels by mid-century (see references below). Moreover, the IEA has shown that there is enough potential to phase out coal and to replace it with sustainably grown biomass. In short, all those who take climate change serious, could have an interest in supporting negative emissions bioenergy.

German giants Siemens and E.ON Energie are the latest to cooperate on the development of an economic and efficient method for carbon capture. They announced that their starting point is a solvent with special characteristics which provide the basis for a new process to capture CO2 from the flue gases of power plants (post-combustion capture - can be applied to biomass flue gas). A pilot installation on an E.ON power plant site in Germany will be operational by 2010. Further developments will follow up until 2014. The mid-term target is to develop this new CO2 capture process ready for large-scale, commercial deployment by 2020. The project is being funded by the German Federal Ministry of Economics and Technology (BMWi) within the framework of the COORETEC initiative.

One of the most promising CCS technologies is post-combustion CO2 capture. The goals are development of advanced ecologically compatible CO2 solvents, optimization of the capture process and intelligent integration into the power plant. The real challenge is to attain high power plant efficiency and to avoid negative impact on the environment, for example, by emitting solvent. - Tobias Jockenhoevel, head of the innovative power plant concepts division and project manager at Siemens Energy

The new process and the energetically optimum integration into conventional power plants will be verified in 2010 in a small pilot plant under real operating conditions, with particular considerations of the significance for a full-scale plant. The new process will not only be feasible for new power plants, but it will also be appropriate for retrofitting existing plants, which opens up significant application potentials worldwide.

The latter point is important in order to imagine a scenario for the emergence of BECS systems. Coal-fired power plants will first start to co-fire biomass, which is already being done routinely and on a large scale throughout Europe. Then they will transit to co-firing ever more biomass - Britain's Slough Heat & Power CHP plant is already using 87% biomass in a plant that started out with coal alone, proving it can be done -, a prospect that becomes ever more likely because coal prices are increasing rapidly and biomass supply chains are becoming more efficient. Finally the power plants are retrofitted with carbon capture technologies, like the ones being developed by Siemens and E.ON. This would be a feasible, safe, reasonable but nonetheless radical scenario that would offer the single most important contribution to reducing global carbon emissions:

Bernhard Fischer, Chief Technology Officer, member of the executive board of E.ON Energie, says E. ON brings into this partnership its experience from the planning and operation of numerous fossil-fueled power plants and the site for the planned pilot plant, whereas Siemens in turn provides extensive experience and know-how in the engineering and project execution for complete power plants. Siemens also brings in chemical process development competencies and engineering skills of the former Hoechst AG. Those look like interesting preconditions for successful development of an efficient CO2 capture process, as well as for its optimum integration in a power plant process.

Michael Suess, CEO of the Siemens Fossil Power Generation Division, says that even in the foreseeable future, it will not be possible to meet the rapidly growing demand for electricity worldwide without fossil fuels such as coal and natural gas [we disagree: projections by the IEA and by the Abrupt Climate Change Strategy Group, which studies BECS systems, show sustainably produced and internationally traded biomass can replace all coal consumption, and be used in negative emissions power plants.]

Climate experts agree, continues Suess: CO2 emissions have to be reduced quickly and significantly to limit the increase in temperature. For that a broad variety of technologies has to be implemented. This includes technologies to further increase the efficiency of power plants and processes to capture and store carbon dioxide (CCS), added Suess. Just under a quarter of global CO2 emissions are attributable to power generation. It is anticipated that viable large-scale CCS technologies will capture approximately 90% of the CO2. Within the EU, mandatory carbon dioxide capture and storage is being debated for beyond 2020. For this reason new solutions have to be developed and tested today.

Joerg Kruhl, head of the new technologies division at E.ON Energie, says that besides the mid-term development of beneficial technologies, the fast transfer of promising post-combustion capture processes to real power plant operation is what counts in particular for E.ON today. This is the necessary next step on the way toward large-scale deployment of CCS in the energy sector.

http://biopact.com/2008/01/siemens-and-eon-to-cooperate-on-post.html

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