Filters
Gases Emissions during Composting Process of Agri-Food Industry Waste
The vegetable production is an important part of agriculture sector in every country. In Poland, vegetables and fruits production covering the area of no more than 3% of agricultural land, is more than 36% of plant production and 14–15% of the whole agricultural production. The study aim was to determine the management possibilities of the selected waste from vegetable production in composting process. Laboratory tests were carried out using the bioreactor set-up with capacity of 165 dm3, respectively, for each chamber. The composting process has been tested for the following mixtures: K1—cabbage leaves, tomato dry leaves + manure and slurry additive; K2—cabbage leaves, solid fraction from biogas plant + manure and straw additive; K3—cabbage leaves, onion husk + straw additive. In all three composts the thermophilic phase occurred which indicates that the process ran correctly. In each chamber, the temperature exceeded 70 °C and its maximum value during the experiment was 77.5 °C for K2 compost. The article discusses changes in O2, CO2, NH3 and H2S emissions during composting. The carbon dioxide concentration in the exhausted gas from analyzed composts and the ratio with oxygen they testify to the decomposition of raw materials in the composting process. The results showed that the agri-food waste can be a proper substrate for composting production. Due to legal regulations and the increase in prices of mineral fertilizers, the development of the compost market should be expected.
Research on a New Method of Water Recovery from Biogas Plant Digestate
Digestate is a product with valuable fertilizing properties, remaining after the anaerobic fermentation process. An essential feature of the substance in question is its high water content of up to 97%. To improve the fertilizer value of the digestate, it is necessary to dehydrate it to produce a concentrated product. This paper determined the possibility of dewatering the digestate using an innovative reactor design. The study, conducted on a laboratory scale, used digestate from a Polish biogas plant. The dewatering technique described in the paper is based on the evaporation and condensation of water vapor on the inner surface of the reactor dome. The condensate accumulated on the leach trough and was directed to a storage tank. During the weeks of testing, 11.5 kg of condensate was separated from the initial weight of the digestate (32 kg), with a dry weight of 6.11%. The resulting condensate from dehydration had an average pH value of 9.0 and an average ammonium nitrogen content of 2.07 g∙kg−1. The economic calculations made in the paper allowed for estimating the expected savings associated with the management of digestate in Poland. The research showed the proposed technology’s high potential for dewatering digestate under laboratory conditions.
Sustainable Use of Digestate from Biogas Plants: Separation of Raw Digestate and Liquid Fraction Processing
This review provides an overview of the various aspects involved in the digestate separation process with a focus on the best solution. The paper discusses the possibility of processing the liquid fraction using membrane separation processes and evaporation. Despite the identical goal of digestate separation, the solutions presented have many differences. These differences affect each process’s capital, operating costs, efficiency, and complexity. Among the selected solutions, the most popular technology for separating digestate is a screw press. Its advantage is the simplicity of its design compared to the centrifuges or filter presses used. In addition to the economic aspect, a definite advantage of mechanical separation is the possibility of using the liquid fraction to reduce the dry matter of the feedstock for biogas plants. Regardless of the chosen technology, striving for the closed-cycle operation of biogas plants and optimizing production processes is now becoming necessary. Proper management of the digestate is a crucial element of the operational efficiency of any biogas plant in case of the sustainable energy. The prepared article will fill some gaps in knowledge and indicate further directions of action. It is necessary to further develop research on methods of digestate separation.
Sustainable management and recycling of anaerobic digestate solid fraction by composting: A review
Anaerobic Digestion and Composting as Methods of Bio-Waste Management
Abstract The management of biodegradable waste from various sectors of economy is an essential element in terms of environmental protection. The paper discusses issues related to the possibility of bio-waste treatment using anaerobic digestion technologies and composting processes, highlighting the conditions for the processes and their advantages and disadvantages. The challenges of overproduction of bio-waste faced by highly developed countries around the world are also presented. Research showed that the anaerobic digestion of this waste combines both biofuel production and a circular economy. The popularity of this method is linked, among others to a low cost of raw materials and wide range of possible uses for biogas (i.e. electricity, heat, or biomethane). In addition, an alternative bio-waste management option, compost production, was discussed. The study aimed to compare anaerobic and aerobic bio-waste management processes.
Economic and Energy Efficiency Analysis of the Biogas Plant Digestate Management Methods
The aim of this study was to conduct a comprehensive economic and energy efficiency analysis of selected digestate management methods, considering their implications on operational costs and resource management. To achieve this aim, the study focuses on a comparative assessment of different digestate management methods, including land application, mechanical separation, the composting process and pellet production. The economic analysis involves the evaluation of the initial investment, operational expenses, and potential revenue streams associated with each method. The most economical and popular solution of digestate management is direct use as fertilizer, with total costs of 1.98 EUR·Mg−1. All of the other methods involve higher digestate management costs, respectively; for separation it is 2.42 EUR·Mg−1, for composting it is 2.81 EUR·Mg−1. The process that is the most energy-intensive, but profitable, is the production of pellets from digestate, resulting in profits of 334,926 EUR·year−1. It should be noted that the other analyzed methods of digestate management also bring many environmental benefits, affecting sustainability and reducing emissions. The results of this research will contribute unique data on the feasibility of managing the digestate and its fractions. The calculations of economic and energy values for different strategies will allow for the optimization of the overall performance of the biogas plant, thus promoting a circular economy.
Characteristics of Substrates Used for Biogas Production in Terms of Water Content
New technologies based on the anaerobic digestion process make it possible to manage problematic waste. Methane efficiency depends largely on the level of the hydration of the substrates used for biogas production and their ability to decompose easily. The aim of this study was to present the current state of knowledge and practices in substrate hydration characteristics, focusing on pretreatment methods as the preferred method for improving efficiency. The paper discusses issues related to the degree of hydration of substrates in the context of their use in biogas plants. Reference was also made to topics related to the transportation and logistics of raw material supply regarding environmental impact. Biogas plant projects should be expanded to include an element related to assessing the impact of raw material deliveries on the immediate environment. Previous papers have not sufficiently analyzed the aspect related to the hydration of substrates used in anaerobic digestion processes. The presented and discussed research results can be implemented to optimize biogas plant water management processes. By replacing standard feedstock transportation methods with a pipeline, the environmental impact can be reduced by nearly ten times.