Text by Angelo Ausiello (UNINA), Adelaide Calbry-Muzyka (PSI) and Serge Biollaz (PSI)
Switzerland has a considerable but under-utilized bioenergy potential in the form of manure. This manure originates primarily from cattle. It is distributed across many small farms. In 2015 the average animal density was 24 animals (GVE) per farm. The small size and decentralized nature of these manure sources result in challenging questions: How do we make best use of Swiss manure for energy use at a scale of 2-75 kWe. What limiting conditions prevent the use of this energy source? By which means can farmers be encouraged to implement energetic use of manure? What technology chains are most promising? These questions are addressed by a SCCER BIOSWEET team consisting of several independent research groups and external partners.
At this early stage of the study, the scope of the Manure-to-Electricity project is focused on developing concepts for value chains that make such technologies attractive for Swiss agriculture. The development of such technology involves several technical features and an adequate “technology supply chain” to the market.
The Manure-to-Electricity team in SCCER BIOSWEET was assembled from research groups with an expertise in each of the key areas needed to develop this value chain. A detailed assessment of Swiss manure resources is provided by Vanessa Burg from the WSL. On a technical level, several process steps are necessary to generate electricity from manure. Manure can be easily converted to biogas by anaerobic digestion processes, which is the research area of Prof. Urs Baier’s group at ZHAW. At the current state of the project the operating conditions of a small size digester have been selected and several companies have been identified in the international market, which can supply such small scale digesters.
The quality of biogas is a key point since several harmful compounds, even in trace amounts, can irreversibly damage the electricity generation unit (fuel cell, internal combustion engine). With support from the group of Dr. Serge Biollaz at PSI, a clean-up system has been evaluated and several adsorbing materials have been identified to remove such compounds up to the concentration limits defined by fuel cells. The final step is to convert this biogas to electricity. The use of solid oxide fuel cell (SOFC) technology for the production of electricity (2-5 kWe) from agro-biogas has been assessed by a research group at EPFL, led by MER Jan Van herle. Several fuel cell companies have been identified in the European market as potential suppliers.
An ongoing difficulty concerns the economics and cost structure of such a system. This is an issue which can only be resolved by close collaboration between technology experts, Swiss farmers, and research groups. A review of the cost structure and possible revenues is the focus of the next stage of analysis.
The SCCER BIOSWEET-team is perfectly positioned to initiate this dialog. In the end, the project “Manure to Electricity” should lead to better “waste to energy” processes that allow to reduce the use of fossil fuels and greenhouse gas emissions by the use of renewable sources that exist already today in Switzerland. In the short term this joint effort should lead to a smart pilot and demonstration project, which validates the outcome of the ongoing study. Ultimately, electricity generation from biowaste in this way could raise its contribution to the Swiss electricity supply from currently 0.5% to 5%, additionally recovering some useful heat.