Anaerobic digestion of agro-industrial waste is of significant interest in order to facilitate a sustainable development of energy supply. Using of material and energy potentials of agro-industrial waste, in the framework of technical, economic, and ecological possibilities, contributes in increasing the share of energy generated from renewable energy sources. The paper deals with the benefits arising from the utilization of biogas produced by co-digestion of whey and cow manure. The advantages of this process are the profitability of the plant and the convenience in realizing an anaerobic digestion plant to produce biogas that is enabled by the benefits from the sale of electric energy at favorable prices. Economic aspects are related to the capital cost (€ 2,250,000) of anaerobic digestion treatment in a biogas plant with a 300 kW power and 510 kW heating unit in a medium size farm (450 livestock units). Considering the optimum biogas yield of 20.7 dm(3) kg(-1) of wet substrate and methane content in the biogas obtained of 79%, the anaerobic process results in a daily methane production of 2,500 kg, with the maximum power generation of 2,160,000 kWh y(-1) and heat generation of 2,400,000 kWh y(-1) The net present value (NPV), internal rate of return (IRR) and payback period for implementation of profitable anaerobic digestion process is evaluated. Ecological aspects related to carbon dioxide (CO2) and methane (CH4) emission reduction are assessed.

No abstract

The production of renewable energy, a reduction of waste and prevention of environmental pollution promote the industrial application of anaerobic co-digestion for the treatment of agro-industrial organic waste. In this paper production of biogas/methane was studied by performing a series of laboratory batch experiments using whey and cow manure as substrates. The influence of substrate concentration, temperature and pH on biogas production was analysed. A mathematical model has been developed that describes the co-digestion process. The hydrolysis of proteins, lipids and cellulose has been modelled using first-order kinetics. Fermentation of sugars and amino acids, anaerobic oxidation of long chain fatty acids (LCFA), acetogenesis and methanogenesis have been described using an unstructured model based on Monod kinetic equations taking into account different inhibitory effects. Model applicability was demonstrated by comparing experimental results with the model simulation results.

No abstract

The climate change policy is one of the key factors in the achievement of sustainable development in the Republic of Croatia. Control and mitigation of greenhouse gases is correlated with all economy activities. Waste management is one of the main tasks of environmental protection in Croatia. The Waste Management Strategy of the Republic of Croatia and the Waste Management Plan in the Republic of Croatia define the concept of waste management hierarchy and direct and indirect measures as criteria for sustainable waste management establishment. The main constituent of this system is avoiding and minimizing waste, as well as increasing the recycling and recovery level of waste and landfill gas, which also represent greenhouse gases mitigation measures. The Waste Management Plan consists of several direct and indirect measures for greenhouse gases emission reduction and their implementation also affects the greenhouse gases emissions. The contribution of the methane emission from landfills amounts to about 2% of the total greenhouse gases emissions in Croatia. The climate change control and mitigation measures as an integral part of waste management sector strategies represent the measures of achieving the national objectives towards greenhouse gases emission reduction which Croatia has accepted in the framework of the Kyoto Protocol.