Maturity analysis of compost produced from co-composting of vegetable solid wastes with sawdust

Abstract

Municipal Solid Waste (MSW) consists the everyday household items that are discarded by people and with rapid growth of population and economic development, generation of such waste has also increased tremendously. In developed countries, Municipal Solid Waste (MSW) consists higher amount of inorganic wastes than in developing and low income countries. Hence management of solid wastes is different for developed and developing countries. It can be found that in developing countries, higher amount of organic wastes (food, paper, kitchen waste etc.) consists solid wastes and as a result composting is an ideal option for resource recovery from such wastes. In this research, an effort was made to convert vegetable solid waste (VSW) into fertilizer by composting and co-composting for 60 days with saw dust (SD) at three different ratios VSW : SD = 100 : 0, VSW : SD = 80 : 20, VSW : SD = 60 : 40. For a compost to be applied as fertilizer, stability (resistance for decomposition) and maturity (ready to use) should be analyzed so that the compost does not cause any adverse effect on plant growth. From the literature review, it was found that many indices are there to measure stability and maturity of compost samples. This study determined and compared few stability; maturity indices from those available ones to find out the set of most reliable tests. From the results, it was found that C/N value cannot be used to asses stability when saw dust is used because of the presence of non-compostable lignin which may cause nitrogen deficiency. Also pH, microbial activity, reduction in organic matter (ROM) values were measured, but it is concluded that each of these parameters alone cannot define stability of compost samples. On the other hand, CO2 evolution of compost sample showed a better result to predict compost stability and it was also found that the results were very similar to the plant growth test values. For maturity evaluation, NH4 +-N:NO3 --N ratio and plant growth tests provided better results, however germination index (GI) and electrical conductivity (EC) measurement did not show consistent results to predict maturity. Hence those tests cannot be used alone to assess maturity. Lastly, it was suggested that only one test cannot be used to evaluate stability and maturity, rather it is wise to use a combination of these tests to get better judgment of compost stability and maturity. Apart from these tests, produced compost was compared for its effectiveness with commercially available organic and inorganic fertilizer and the result showed that compost samples proved to be better than inorganic fertilizer and commercial organic waste in most of the cases.