Abstract

The maritime transport sector is currently highly dependent on oil-based fuels. International regulations enforce tight limits regarding NOx emissions from the exhaust gases and maximum sulphur content in the fuel, enhancing the sector interest towards the development of cleaner alternative fuels. A transition to biomass-based liquid fuels is of interest as a common solution for reducing pollutant emissions and for CO2 emissions mitigation. In this paper, a case study on Sweden analyses the potential of methanol production, using gasification of woody residues from sawmills to cover domestic and international maritime energy demand. Methanol seems to be a promising alternative to heavy and light fossil oils as maritime fuel, and sawmills residues are an abundant resource in Sweden. The study considers the entire methanol production chain, starting by assessing the availability of sawmill by-products and ending with the energy demand of final users, identified as the Swedish ports. The analysis considers two scenarios until year 2035, assuming different share of energy demand covered by methanol. When considering the production and use of biofuels, the cost for transportation of the feedstock and the final product have a great impact on the final cost. An optimization model is used to locate the methanol production plants, so to minimize the cost of the production chain. Four possible plant sizes are considered, 100, 200, 300 and 400 MW of biomass fuel thermal input. The production plant is modelled to determine the material and energy streams involved in the process and to obtain the cost and efficiency of producing methanol at the synthesis plant. The results include the final methanol cost and an estimation of the CO2 emissions reduction potential from replacing oil fuels with methanol for the assumed scenarios. "p"QC 20200616

Abstract

In spite of being a process that exploits a renewable source of energy, the combustion of wood-based biomass contributes to deteriorate outdoor and indoor air quality. Critical situations for human exposure may occur in mountainous areas, where wood-based biomass is usually abundant and the complex morphology may favour the stagnation of air pollutants in valleys. Replacing wood/pellet stoves with centralised systems would reduce the impact, but the construction of district heating systems may not be convenient in areas with low density of houses. A possible solution could rely on direct electrical heating (DEH) systems, preferably fed by thermochemical processes that help achieve environmental goals for the local community, like the reduction of waste landfilling and the valorisation of the energy content of waste. This paper aims at presenting a comparison between the impacts expected by household wood/pellet stoves and by a modern waste-to-energy (WtE) plant, in terms of emissions of air pollutants into the atmosphere, when replacing wood stoves with a DEH system fed by the electric energy generated by the WtE plant. The comparison shows that the replacement of household stoves with an equivalent DEH system would be beneficial in terms of impacts on the local air quality. Such an approach could be considered to reduce the health impacts from biomass burning in critical areas like the Alpine region.