Decentralized Biogas Production in Urban Areas: Studying the Feasibility of Using High-Efficiency Engines

Abstract

The study examines decentralized waste treatment in an urban setting with a high-density population of 2500 inhab./km2. The co-digestion of food and garden waste was assumed by using several mid-size digesters, while centralized biogas and digestate valorization was considered. The studied configuration generates electricity and thermal energy, covering 1.3% of the residential electricity demand and 3.2% of thermal demand. The use of double-turbocharged engines under the most favorable scenario aids cities in reaching sustainability goals. However, the location of treatment plants is a factor that may raise social discomfort and cause a nuisance to citizens. Locating waste plants near residential areas causes discomfort due to possible odors, gaseous emissions, and housing market distortions. Such problematic aspects must be addressed for the decentralized alternative to work. These factors are of great relevance and must be given a practical solution if the circular economic model is to be implemented by considering the insertion of waste streams into the production system and generating local energy sources and raw materials.

Assessing Digestate at Different Stabilization Stages: Application of Thermal Analysis and FTIR Spectroscopy

“…Conversion into organic acids and subsequent degradation into methane follow a diversity of microbial pathways [9,10], ending with biogas as the product of interest and digestate as a residual by-product. Several digestion configurations have been proposed, including centralized and decentralized centers, partial decentralization by performing the initial digestion stage in small units and centralizing the subsequent digestion phase, or centralizing only the valorization of biogas after the initial digestion stage [11][12][13][14]. Regardless of the configuration option selected, a practical solution for the final disposal of digestate is necessary.…”