It has been an increased interest in using sewage sludge as agricultural fertilizer and soil improvement material, especially as compost with biomass. This paper analyses five samples of composts from bio waste and sewage sludge, with various percentage of sludge, using the following parameters: pH, EC, carbohydrates content, enzymes content and C: N ratio. The results were correlated with FT-IR spectra and germination test in order to assess the stability and maturity of the composts samples. It was also calculated the composition efficiency of compost samples. All tests indicate a favorable environment for microorganisms and a good conversion to complex compounds: amino acids, carbohydrates and products of their biodegradation amines, amides, carboxylic acids, aldehydes, ketones, enzymes, proving they can act as bio fertilizers.

Our research was focused on developing some new procedures to reduce the biodegradable wastes by composting. The aim of this study was to obtain and asses at laboratory scale the maturity of three compost samples of different proportion of vegetable waste, beech sawdust and sewage sludge by analyzing their FT-IR spectra and C/N ratio. The composting process was monitored by tests performed weekly on the three samples in order to investigate the physical parameters (pH and electroconductivity EC) and chemical parameters. Thus, organic N was determined as aminic N from amino acids content and as total organic N content. Organic C content was determined as monosaccharides content and TOC content. The results were also confirmed by C/N ratios. At the end of the composting process germination tests were performed for 7 days and the GI were determined. All the lab tests showed that the maturity of composts was achieved in all three samples, proving also that sawdust acts as an inhibitor of the activity of microorganisms in the decomposition of complex compounds and the sludge contributes to the improvement of their activity by the addition of nutrients.

Among the biofuels produced nowadays in the world, biodiesel became more and more attractive thanks to its advantages compared with petroleum-based diesel: (a) reducing the dependence on petroleum; (b) reduction of most exhaust emissions; (c) biodegradability; (d) higher flash point, leading to safer handling and storage; (e) excellent lubricity. However, the neat vegetable oils used in biodiesel production determine a higher price of biodiesel compared with petroleum diesel price. Waste cooking oils can be alternative raw material for biodiesel production especially because of its low cost, high availability and benefits of environmental protection. The research presented in this paper aimed to establish: (a) simple methods for monitoring the synthesis of biodiesel by transesterification of two different waste cooking sunflower oils with methanol using NaOH as catalyst, in comparison with neat sunflower oil and (b) the characteristics of oils and biodiesel obtained, comparative with characteristics described for biodiesel by the standards ASTM D6751 and EN 14214. The results obtained showed that during biodiesel synthesis, the saponification value decreased both for sunflower oil and waste cooking oils due to transesterification reaction of lipids from oils and formation of methyl esters. The values of physical and chemical characteristics of biodiesel were much smaller than those for neat and waste sunflower oils, especially viscosity, saponification value and acid value. The characteristics values of biodiesel obtained from waste cooking oils were better than characteristics of the petroleum diesel (standard EN 590), and they fit within ASTM D6751 and EN 14214 standards, which indicate that the obtained biodiesel samples could be used in engines without other modifications.

Composting is nowadays an important and efficient process in sustainable organic waste management. Recycling process of biodegradable organic waste (animal and agriculture residues, sewage sludge, household refuse) by composting, also represents an ecological solution to synthesize new materials used as biofertilizers or adsorbents in wastewater treatment. The paper presents results obtained in composting vegetables waste, sewage sludge, beech sawdust and beech ash, monitoring the parameters of the composting process and investigation of the nutritional quality of the compost by germination test.