The implications of management practices on life cycle greenhouse gas emissions in biogas production.

Biogas production is seen as one of the key measures in circular economy providing several benefits for the environment. In practice, however, these benefits may not be achieved if the production is not implemented and managed in ways that reduce gaseous emissions. Thus, this study aimed at highlighting how different management practices impact the climate during the life cycle of biogas production in comparison to management without biogas production (reference). Advanced, more emission-reducing practices resulted in 97-107% and conventional practices in 57-75% less emissions when biogas was utilized as transport fuel. If biogas was utilized in CHP (combined heat and power production), the emission reductions were 67-74% and 13-30%, respectively. This reflects the fact that inefficient practices can lead to minimal emission reduction without achieving the desired climate benefit in comparison to the reference. On the European level, this may also mean that the emission reduction demands of RED II (Renewable Energy Directive) regulation are not met. Therefore, when supporting biogas production with public funds, assurance of using emission-reducing practices should be made a prerequisite.

To separate or not? A comparison of wastewater management systems for the new city district of Hiedanranta, Finland.

In this study, life cycle assessment (LCA) and life cycle costing (LCC) methods were applied for the new city district of Hiedanranta, where source-separating sanitation systems are being considered. Two source-separating systems were compared to the conventional sanitation system with a centralized wastewater treatment plant (WWTP). With a separating system, three to 10 times more nitrogen could be recovered compared to the conventional system. If the nutrient potential of the reject water of the sludge digestion were to be utilized, the recovery rate would be even higher. For phosphorus, the recovered amount would be at the same level for all the alternatives. However, the plant availability of phosphorus is higher in separating systems. Based on the environmental impacts of separating systems with improved nutrient recovery, the climate and eutrophication impacts could be reduced, but the acidification impact may be higher. However, the actual climate benefits depend on how the avoided emissions will be realized, which is highly dependent on the policy and decision-making processes in the society. The life cycle costs of the alternative source-separating systems are higher at current prices. Source-separating sanitation produces new recycled nutrient products of human origin that contain fewer contaminants and could therefore be more easily accepted for end use when certain boundary conditions are met.