Biogas Potential in the North of Sweden : Inventory and Techno-Economic Assessment of Substrates for an Increased Biogas Production in Norrbotten

Sammanfattning: Great investments are planned in the north of Sweden the coming years, not the least in the county of Norrbotten where the projects collectively are referred to as the green transition due to the focus on fossil-free techniques. But to be able to secure a sustainable energy supply and reach the goal set by the member states of the European Union of a carbon dioxide neutral union in 2050 the production of alternative energy sources needs to intensify. The continuous phaseout of fossil energy and increased electrification, of society as well as industry, place heavy demands on the energy supply, meaning that all non-fossil energy sources become important and should increase its production to meet the ever-increasing effect need. One energy source that is produced from renewable sources and can be directly interchanged with natural gas is the methane fraction of biogas. Biomethane is currently mostly used as a vehicle fuel in Sweden but that can be subjected to change and for example become an important source of hydrogen or be used for fossil-free steel production in the north of Sweden. This thesis explored the availability of potential local substrates for biogas production in the county of Norrbotten, with certain focus on Luleå municipality. The work was performed in collaboration with Lumire (Luleå Miljöresurs AB), a municipal company that mostly produces biogas from wastewater treatment sludge and is responsible for water and sewage, as well as waste collection and recycling within Luleå. An inventory was compiled, and potential substrates evaluated in order to select two specific substrates for a techno-economic analysis with the purpose to assess energy inputs and connected costs related to the implementation of new substrates along with the potential biogas production. The energy balances included the potential energy yield, the energy consumption from the generation of the substrate, transport to the bio-gas plant, and pretreatment and was calculated for different scenarios. The effect that a biogas loss of 9.5% had was also included. Alongside the costs for the energy consuming activities, the investment cost of a pretreatment equipment was also estimated. The inventory of substrates showed that there is suitable organic material, such as manure and food industry waste, in the region but that a small amount could be considered available today as much is currently used, if not for biogas but as animal fodder and for ethanol production. The share of productive farmland has decreased in Norrbotten over time and the disused or unutilised arable land revealed a potential source of biogas substrates. The most common crop today is ley which is grown to be used for husbandry. Meat and dairy are important industries in the north and the inventory showed that 11–16 m3 of blood from local slaughterhouses are generat-ed each week and sent out of the county and to Skellefteå to be turned into biogas. Due to the “export” of a local substrate and the existing unused farmland, ley crops and slaughterhouse blood was chosen as model substrates. The techno-economic analysis showed that the production of ley crops accounted for the main cost and energy input compared to transport and pretreatment. In total, the activities could amount to 25–46% of the potential energy yield. The cost to be covered was around 10 SEK/kg of fuel gas under the used assumptions. The estimated cost of the investment of an extruder was just over one million SEK compared to 790 000 SEK in 2015. The evaluation of slaughterhouse blood excluded the generation of the blood and focused on the transport and pretreatment. The result showed that the suggested pretreatment technique of pasteurisation stood for the main share of the cost, no matter the transport distance, but that the energy input of the transport accounted for 60% of the total energy input at a transport distance of 140 km, which is the current transport distance. Combined, the activities could consume 45-60% of the total potential energy yield from the biomethane production. Costs to be covered varied between 9 SEK/kg fuel gas in the most energy-demanding scenario down to 2 SEK/kg fuel gas in the least costly scenario. The investment in a pasteurisation facility using district heat-ing as the heating medium was estimated to 4.8 million SEK when dimensioned after a dilution of the highest blood delivery. Furthermore, the surface of heat exchangers as an alternative to pasteurisation tanks were estimated, showing that the required surfaces were small, around 1 m3. The conclusion was drawn that a pasteurisation facility risks becoming equipment intensive seen to the amount of substrates. Generally, the results show that there are energy winnings from both substrates but that it is dependent on the activities in the value chain of the substrates. Implementation of ley crops demand that a business model is developed in collaboration with current landowners and that the position and amount of available farmland is mapped. The local usage of slaughterhouse blood would decrease the diesel consumption of the transport but risk becoming equipment-heavy seen to the relatively limited amount of substrate.