Intensified Integrated Bio-Refinery

Lead Research Organisation: NERC Centre for Ecology and Hydrology
Department Name: Hails

Abstract

The most important and urgent global issue is the establishment of sustainable energy and chemicals feedstock technologies to replace the corresponding fossil fuel based technologies so as to achieve a drastic reduction of atmospheric green-house gases. This colossal task is only possible if we utilise biomass either in the form of waste or energy crops since unutilised biomass will degrade and still produce green-house gases. As regards availability, energy equivalence of biomass produced globally is some 8 times the total global energy need. However, unlike fossil fuels, biomass is widely distributed near the population centres. Hence, biomass logistics may sound to be disadvantageous since their collection for conversion at a central (existing) large scale facility will not be economical. Since the products from biomass themselves (electric power or transport fuel) will have to be distributed, biomass logistics is in fact an advantage, provided we address the problem of 'economies of scale'; that is, it is more cost effective to have processing using very large capacity plants. This drawback is remedied by adopting two new technology concepts: Process Integration and Process Intensification. Integration will provide us with energy and resource efficiency while Intensification will eliminate 'economies of scale' since intensification delivers reduced capital and operating costs (due to drastic reduction in plant size), safety, responsiveness and social acceptability. Similar to the concept of oil-refinery, biomass can be converted to high value (therapeutic) chemicals, the remaining residual biomass is converted to bioethanol through a fermentation process, the residue from which is gasified to obtain syngas. Bioethanol is a highly versatile chemical which can be used as liquid transport fuel, as means of chemical hydrogen storage or as a chemical intermediate for higher chemicals such as plastics or drugs. The intensification element will be present at every level, including the extraction process. Bioethanol production through fermentation is a well known route but it will be intensified by using genetically enhanced bacteria and compare the result with wild type. Genetically enhanced bacteria will be contained within special reactors and the physiological stresses will be controlled at microscopic scale which results in further enhancement of the fermentation productivity. Hence, such technology can be applied to other bioconversions such as drugs. Biomass waste such as municipal solid waste, sewage sludge or agriculture residues can also be converted directly to bioethanol via via gasification which produces syngas which must be cleaned and its composition should be controlled and where necessary gases should be separated into its components (hydrogen, carbon monoxide, methane, carbon dioxide) so that they could be used as chemical building blocks of larger molecules such as ammonia, ethanol and methanol. Alternatively, syngas can be used as a fuel for internal combustion engine or fuel cells to generate electricity. These operations should be carried out at high temperatures to enhance efficiency. Syngas-to-power/higher chemicals conversions also require catalytic reactions. However, syngas is essentially a 'dirty' fuel and must be cleaned from tars, toxic components and particulate matter. We will prepare novel 'intensified' high temperature catalysts where the catalytic sites are accessible through a network of pores, like it is in nature, i.e., lungs and kidneys. Bioethanol is not only a good fuel for cars, it is also a good storage of hydrogen and it can be converted to other chemicals such as commodity plastics, ie, polyethylene. The demonstration of bioethanol as an intermediate chemical will be given.

Publications

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Ángel Siles López J (2010) Biorefinery of waste orange peel in Critical Reviews in Biotechnology