Zoltán Gabnai

By Attila Bai and Zoltán Gabnai

Large-scale sewage plants in large cities are suitable for the production of large quantities of biogas, using economically viable biogas upgrading technologies and generally available public transport fleets of a sufficient number of local buses, as well as municipal vehicles. The conditions for the sale of locally produced CNGs do not depend on gas suppliers, they can be very well integrated with local waste management, and the local emission reductions occur in the inner city, where air pollution is the most serious problem. At the same time, the cogeneration solution currently of decisive importance for wastewater plants is more economically and environmentally advantageous in the production of biomethane. The consumption of heat and electricity by these plants is significant and must be supplied through the purchase of biomethane. However, for the local authority, when converting diesel buses, compressed biomethane (CBM) offers much greater savings, so at the municipal level, the process is economically profitable. The short-term spread of CBM (due to the small number of filling stations) is bound to local systems. If more and more cities operated a similar system (allowing refuelling within a few dozen kilometres), it would be expected that passenger cars would also be more widespread.

Part of the book: Transportation Systems Analysis and Assessment

By Attila Bai and Zoltán Gabnai

In this chapter, we present the opportunities and general importance of woody biomass production (forests and short-rotation coppices) and waste management in a common system. Wastewater and different forms of sewage sludge, as energy- and nutrient-rich materials, can contribute to reaching resource efficiency, savings in energy, and reduction of CO2 emissions. Within certain limits, these woody plantations are suitable options for the environmentally sound disposal of wastewater and/or sewage sludge; in addition, they can facilitate the realization of full or partial energy self-sufficiency of the wastewater plant through bioenergy production. Focusing on circular economy, we introduce the aspects of the treatment process and the sizing issues regarding the municipal wastewater treatment and the woody biomass in a complex system. Based on a specific case study, approximately 826 ha of short-rotation coppices (with a 2-year rotation) are required for the disposal of sewage sludge generated by a 250,000 population equivalent wastewater treatment plant. If we look at the self-sufficiency of its energy output, 120–150 ha of short-rotation coppices may be adequate. This complex system can replace the emissions of around 5650 t of CO2 through electricity generation alone and another 1490 t of CO2 by utilizing the waste heat.

Part of the book: Forest Biomass