Anders Ådahl

Process industry energy retrofits: the importance of emission baselines for greenhouse gas reductions

Fuel combustion for heat and/or electric power production is often the largest contributor of greenhouse gas (GHG) emissions from an industrial process plant. Economically feasible options to reduce these emissions include fuel switching and retrofitting the plants energy system. Process integration methods and tools can be used to evaluate potential retrofit measures. For assessing the GHG emissions reduction potential for the measures considered, it is also necessary to define appropriate GHG emission baselines. This paper presents a systematic GHG emission calculation method for retrofit situations including improved heat exchange, integration of combined heat and power (CHP) units, and combinations of both. The proposed method is applied to five different industrial processes in order to compare the impact of process specific parameters and energy market specific parameters. For potential GHG emission reductions the results from the applied study reveal that electricity grid emissions are significantly more important than differences between individual processes. Based on the results of the study, it is suggested that for sustainable investment decision considerations a conservative emission baseline is most appropriate. Even so, new industrial CHP in the Northern European energy market could play a significant role in the common effort to decrease GHG emissions.

Economic and greenhouse gas emissions assessment of excess biomass extracted from future kraft pulp mills

Different studies have shown that the process heat requirements of future pulp mills can be satisfied using available internal biomass (bark and lignin), which are process by-products. Assuming that biomass is CO2 neutral, further reducing the process heat demand will not therefore lead to further reduction of Greenhouse Gas (GHG) emissions - unless the excess biomass is extracted and used elsewhere to substitute fossil fuels. Previous work has demonstrated the potential to extract and export significant amounts of biofuel from future pulp mills. The associated extraction costs can be competitive with conventional forest fuels. However, biofuel extraction reduces the mills potential to cogenerate electric power. This reduced power output must be compensated by increased purchased power from the grid, with associated costs and emissions. Such emissions must be affected to the extracted biofuel, which cannot therefore be considered as CO2 neutral. This paper presents results for costs and associated greenhouse gas emissions for excess biofuel extracted from a pulp mill. The results show that the extraction costs are competitive, but that the greenhouse gas emissions associated with the exported biofuel can be significant and must therefore not be neglected.