The high moisture content present in sewage sludge hinders the use of sewage sludge in incineration or energy application. This limitation of moisture present in sewage sludge can be obviated by using the hydrothermal carbonization (HTC) process. In sewage sludge management, the HTC process requires less energy compared to other conventional thermo–chemical management processes. The HTC process produces energy-rich hydrochar products and simultaneously enables phosphorus recovery. This study investigates the influence of organic acids, inorganic acid, and alkali as additives on phosphorus transformation, yield, proximate analysis and the heating value of subsequently produced hydrochar. The analysis includes various process temperatures (200 °C, 220 °C, and 240 °C) in the presence of deionized water, acids (0.1 M and 0.25 M; H2SO4, HCOOH, CH3COOH), and alkali (0.1 M and 0.25 M; NaOH) solutions as feed water. The results show that phosphorus leaching into the process-water, hydrochar yield, proximate analysis, and the heating value of produced hydrochar is pH- and temperature-dependent, and particularly significant in the presence of H2SO4. In contrast, utilization of H2SO4 and NaOH as an additive has a negative influence on the heating value of produced hydrochar.

Renewable energies – especially wind and solar – have grown remarkably in recent years, but bioenergy is still the most important renewable resource worldwide and in Germany. In contrast to the situation in many other countries, bioenergy in Germany is often based on energy crops. As a result of changing political frameworks, the German bioenergy industry has to use alternative substrates as biogenic waste and residues and to implement more efficient utilization pathways. Biogenic waste and residues can cover in Germany 7 to 9% of the current total primary energy consumption. In the federal state of Mecklenburg-Western Pomerania, more electricity is produced than consumed. This means that the federal state exports electricity to other German regions or abroad, assuming grid bottlenecks do not prevent this. The share of fluctuating wind and solar power is still increasing. Without stabilization by coal power plants, the electrical network could be destabilized by those sources. The presented case study of Mecklenburg-Western Pomerania shows that there are opportunities to contribute to a stable network through the use of bioenergy. Besides the supply of electricity, thermal energy at different temperature levels, as well as fuels for transportation, are also provided by biomass. Around 22% of the annual energy consumption of the federal state could be covered by biogenic waste and residues (based on the technical fuel potential). The figure is currently 7.3%. This shows that there is room to extend bioenergy generation and the use of biogenic waste and residues in the bioeconomy without impacting food production.

A persistent topic of the anaerobic digestion of biowaste is the efficient use of co-substrates. According to Renewable Energy Sources Act the co-substrate input is limited to 10 percent of the average daily substrate feed in Germany. In this concern, the primary focus of this paper is to understand the suitability of crude glycerol in anaerobic digestion of biowaste. Two identical lab-scale anaerobic digester units were added with crude glycerol, and each unit was equipped with four identical fermenters. Unit A was fed with an average organic loading rate of 4.5 kg VS m−3 d−1, and the average organic loading rate of unit B was set at 5.5 kg VS m−3 d−1. The share of crude glycerol in the total feed was 0.77 percent of the fresh matter. The abort criterion is a ratio of the volatile organic acids and buffer capacity (FOS/TAC) in the fermenter above 1.2. The abort criterion was reached after 16 days. In summary, the results lead us to the conclusion crude glycerol is not suitable as a co-substrate for anaerobic digestion for several reasons.

The recovering and recycling of municipal solid waste (MSW) plays a most crucial role in sustainable waste management and environmental preservation. The rapid urbanization and migration of people is urging the bigger cities of china to handle significantly higher amount of waste. Likewise, the overdependence of peri-urban regions like Zhaoquanying town (ZQY) on bigger cities is making the concept of recycling and recovery a major challenge and simultaneously causing a higher burden on urban areas for sustainable waste management. In this concern, it is crucial to make peri-urban regions like ZQY self-reliant in their waste management. The current study provides the integration of experimental analysis and theoretical evaluation to determine the waste value potential of the MSW produced in ZQY. The experimental sorting analysis of MSW in ZQY has revealed that the major component of MSW consists of recoverable waste with an average of 28% (kitchen and other organic waste) and recyclable waste with an average of 20% (paper, plastic, and metal). Despite the having a higher amount of recoverable and recyclable waste, all the produced waste in ZQY is currently ending up in the Shunyi central incineration plant without efficient waste value recovery. The experimental analysis from the organic waste in ZQY has proved to have a higher potential in producing better quality methane and compost. The analysed results reveal that organic waste produced in ZQY has comparatively higher value potential than the recyclable waste available in ZQY, and the total estimated value potential of municipal waste produced in ZQY is between 2.93-3.66 million Yuan/year. The outcome of this study will provide policymakers with the first-hand information and reasoning for directing efforts to achieve waste recovery and recycling in their current waste management practice in ZQY.

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