A smart technology of carbon sequestration by the use of biochar

Abstract

Climate change and decreasing reserves of oil, gas, coal and uranium are a current reality. Therefore, to feed an ever growing world population and to deliver raw materials and energy, biomass needs to be used more wisely. As far as possible, biomass should be used for the production of food rather than for energy and raw materials, which currently tends to be prioritised. Moreover, the remaining biomass, which is not suitable for food production, should be used more efficiently than before. For example, raw materials could also be produced from biowaste, whereby the emerging waste heat could be used further to generate electricity and space heating. Biomass binds the greenhouse gas carbon dioxide until it is digested, rotten or burnt, but may also be transformed into biochar through pyrolysis. Biochar is a material comprising a carbon sink to mitigate global warming. Once applied to the soil it will steadily contribute to the growth of plants for thousand of years. The raw material biochar is produced from biological waste by pyrolysis. Liquid and gaseous mixtures develop as by-products, which, once refined, may be used for a wider range of applications. The development of our pyrolysis technology comprises the following steps: (1) using waste heat to pre-dry the input biomass and to preheat the inlet air, (2) feeding wet biomass, (3) minimizing heat loss by an upright reactor scheme with only a few pipe flanges, (4) testing reactors with upstream as well as with downfall mass flow, (5) flow path through heat zones from 200 up to 800 °C due to the progression of the pyrolysis process, (6) hence biochar extracted from the hot zone showing high quality, (7) directly injecting pre-dried biowaste into the warm zone to suppress unwanted tar by-products and to produce a low-oil synthesis gas, (8) bypass to partly burn syngas for direct heating the hot zone, (9) accurate control of the combustion air flow to optimize the output quantity of the biochar, (10) avoiding movable parts at the reactor to guarantee an operation with low rate of failure, (11) using the evolving syngas to generate electricity, process and thermal heat, (12) restricted converter size to limit the transport distance and use in companies at the waste source and (13) maintenance requiring only minor technical skills in virtue of a simple plant design. At this stage of development, the main objectives of these pyrolysis reactors are production and sale of the produced biochar and the use of the generated electricity within the company. The biomass converters are designed for German and Sri Lankan (communal) enterprise, using mutually beneficial skills and potentials of both countries. Logging slash, lop, greenery from silvicultural measures, saw dust, municipal and food-industrial waste will be processed into high quality biochar.