Techno-economic analysis of wet torrefaction for different feedstocks

According to EU’s Biomass Action Plan, renewable energies are key in helping Europe to achieve its growth and sustainability objectives. Bio-energy is particularly important since it presently accounts for about half of the renewable energy used in the EU. Therefore, innovation and R&D investments in this field are essential for EU to improve competitiveness in the sector and strengthen its position in the global renewable energies market.
The F-CUBED (Future Feedstock Flexible Carbon Upgrading to Bio Energy Carriers) project is an ongoing Horizon 2020 project that aims to develop technology to convert wet biogenic residues into intermediate bioenergy carriers (fuel pellets) via hydrothermal treatment (TORWASH). The project targets feedstocks that are not typically used for energy purposes and are difficult to treat and dispose of. The project aims to reduce this associated feedstock cost by focusing on waste and, therefore on second-generation solid fuels production.
The objective of this EngD project, in collaboration with TNO, is to evaluate the technical and economic feasibility of the F-CUBED concept. This will encompass the development of a flexible process and economics models based on a full-scale commercial deployment of the TORWASH technology.
The feedstocks considered are paper bio-sludge, olive pomace and orange peels. The overall F-CUBED process consists of TORWASH hydrothermal treatment and filter press dewatering, to produce a solid product (converted into fuel pellets via drying and pelletization) and a liquid product (anaerobically digested to produce biogas). This is benchmarked against current practices: respectively combustion of the wet paper sludge stream, olive pomace sales for low-grade oil recovery and composting of orange peels as well as benchmarking for energy generation via anaerobic digestion.
For the technical evaluation, the key performance indicators chosen are the pellet composition and the energy efficiency of the processes. Although the pellets produced from the F-CUBED process cannot be marketed as woody pellets, they can find application in sectors where premium wood pellets are not needed for example in power plants. The F-CUBED scenario is considerably more energy efficient when compared to the Current and Reference scenarios. Across all the feedstocks, the F-CUBED process is 3 to 14 times more energy efficient.
The process models have been used to size process equipment and estimate CAPEX and OPEX. The operating costs are adjusted to account for the regional labor differences, seasonality and the varied waste streams generated. Given the high investments and low revenues from the pellet sales, the standard layout of the process fails to break even compared to current operations. However, in some custom cases, it shows promise. For the paper bio-sludge case, when drying and pelletization were omitted and the solid product is used onsite for energy generation, there is a potential saving of 0.45 million euros per annum. Under a similar custom case, for orange peels, F-CUBED looks promising if in the future the current practices become 5-7 times more expensive or obsolete under new policies. The caveat is that additional fruit and vegetable waste has to be imported so that it can operate for the full year.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 884226.