Tuomas Niskanen’s scientific contributions

The European Union's goal is to increase the share of renewable energy sources to 20 per cent and that of liquid biofuels for transport to at least 10 per cent by 2020. Liquid biofuels for transport are, for example, biodiesel and bioethanol. Their use is not assumed to increase CO2-emissions in the atmosphere. However, production processes of transport fuels need energy causing indirect CO2-emissions. To evaluate the environmental burden of these biofuels it is important to consider indirect CO2-emissions in analyses, too. This study defines indirect CO2-emissions for Digestion process, Bioethanol process, FT-process (Fischer-Tropsch-process) and Bio-SNG-process and compares their environmental burden.

The goal of biofuel production is to partially replace fossil fuels in energy generation and transport. For the evaluation of biofuel production processes different criteria are applied and usually they include costs, efficiency aspects and emissions. However, evaluation of the energy efficiency of biofuels production is difficult since no general standard method exists for that. This paper compares three different assessment methods of energy efficiency both qualitatively and quantitatively. The methods are: thermal efficiency, exergy analysis and primary energy analysis. The feasibility of the methods is tested on a Bio-SNG (synthetic natural gas) production process which was modelled in AspenPlus and MS Excel. The results show that the exergy analysis seems to be advantageous when it comes to detailed (sub-) process analysis whereas the primary energy analysis offers the advantage of showing how the system is influencing the global primary energy resources. The results obtained by the thermal efficiency analysis do not add any new information to the results obtained by exergy and primary energy analyses. Exergy and primary energy analyses should be the preferred means for process assessment. Especially a combination of the two methods could offer the chance to develop a more holistic energy efficiency indicator.

Fossil fuels applied in energy generation-, transport- and refinery processes can be replaced by biofuels. This offers plenty processing options for biomass resources such as thermo-chemical. For process evaluation different criteria is applied, usually including costs, energy efficiency and CO2 emission. However, comparative evaluation of the energy efficiency is difficult since no general standard method exists. The objective of this paper is to compare different methods of energy efficiency and CO2 emission assessment in order to systematically analyse their differences qualitatively and quantitatively. The methods include a general engineering approach, CO2 assessment according to the EU’s Renewable Energy Sources Directive, primary energy efficiency analysis (incl. CO2 assessment) and exergy analysis. In this paper the methods are compared, based on a case study of Bio-SNG generation from woody biomass (simulated with Aspen+). The work shows the differences of the methods when applied to the same process allowing critical discussions of the methods applicability and providing a starting point for the future work on developing novel energy efficiency and CO2 emission assessment methods.