Municipal solid waste is commonly known as garbage or trash which is hazardous refuse generated from different sources such as households, institutions, agriculture and sewage. It can include industrial waste in rare cases.
Municipal solid waste is composed of waste, compostable and recyclable materials. There is a great variation present in the composition of municipal solid waste from municipality to municipality, that changes significantly with time. The change in case of lifestyle pattern, especially in urban areas, has led to increase in generation of municipal solid waste. People clean up their own homes but litter their instantaneous surroundings which affect the community including themselves.
Due of inappropriate disposal system, municipal solid waste heap up on the road sides and become a problem. This type of dumping materials leads to the decomposition of biodegradable municipal solid waste under uncontrolled and unhygienic conditions which produces a very unpleasant smell and breeds several types of insects and infectious microorganisms in these materials.
During the process of collecting wastes, the hazardous wastes usually get mixed with ordinary garbage and other flammable wastes, making the disposal process even harder and risky. It can cause pollution in the surrounding air, badly affect the health of humans, wildlife which leads to negative impact on the environment. Apart from this, it also spoils the aesthetic value of the surrounding area.
Organic municipal solid waste compost
Utilization of municipal solid waste (MSW) is important to curb ever-rising demand of scarce land for its disposal. Common methods of MSW management include recovery for recycling or composting, combustion (with the resulting energy used to generate electricity or steam in some cases) and landfill disposal. Typically, refuse is collected, separated and sent to either a landfill or a municipal recycling center for further processing.
Composting is one of effective method for managing MSW that is a biological process in which micro-organisms, mainly bacteria and fungi, convert degradable organic waste into humus like substance. The final product, which just look like soil, has high concentration of nitrogen and carbon and is a best medium for growing plants, at relatively low-cost, that is suitable for agricultural purposes such as a soil conditioner but as well as a fertilizer. Composting of MSW results in reduction of the volume of the solid waste, killing of pathogens that may be present, decreases germination of weeds in agricultural fields. It also destroys malodorous compounds. It does recycling of the nutrients and returns them to the soil. Apart from clean, cheap and safe, composting can significantly reduce the amount of disposable waste too.
Responses by plant systems range from none to over a two-fold increase in yield. Specific responses are dependent on crop and site
With rising tendency towards organic agriculture, production of organic MSW compost for agriculture is getting attention due to its positive effect on biological, physical and chemical soil properties. Incorporation of composted MSW in soil usually results in a positive and useful effect on the growth and yield of a wide range of crops and results in restoration of ecologic and economic functions of land as well. Responses by plant systems range from none to over a two-fold increase in yield. Specific responses are dependent on crop and site. Useful property of MSW compost is the high organic matter content and low bulk density. Repeated application of MSW compost consistently increases soil organic matter content and soil Carbon / Nitrogen (C/N) ratio to levels greater than those of non-amended soil.
Municipal solid waste compost has a high water holding capacity because of its organic matter content, which in turn improved the water holding capacity of the soil. In case of silt loam, mature MSW compost increases aggregate stability. As far as soil biological properties are concerned. Application of MSW compost increases the soil microbial biomass C and soil respiration, improves the soil ecology which is increasingly being used to evaluate soil quality as well.
Chemical components of MSW
Copious amounts of compost (MSW) are being often used in agriculture to meet Nitrogen (N) requirements of crop and for the addition of organic matter as well in soil nutrients status. MSW compost effectively supplies Phosphorus (P) to soil with soil P concentration increases with increases in application rates. Calcium (K) is available in MSW compost just like mineral K fertilizers. Similarly, the Magnesium (Mn) and Copper (Cu) concentrations in soil increase with addition of MSW compost. This compost increases the soil Sulphur (S) concentrations but decreases with time perhaps due to downward movement in the soil profile.
MSW compost tends to increase total amount of soil Zinc (Zn) and Boron (B) concentrations when compare to non-amended controls. But immature MSW compost tends to have a lower pH prior to thermophilic stage due to the intensive production of organic acids. The lower pH causes certain metals in the compost to have higher water-extractable concentrations. Therefore, it may be possible to mitigate the heavy metal availability by managing the compost pH.
Discussion
Composting of MSW has potential as a beneficial recycling tool. However, its safe use in agriculture depends on the production of good quality compost, specifically the MSW compost that is mature and has lower concentration in metals and salt content. There is a need for the development and implementation of comprehensive industry standards. The effective method of reducing metal content and improving the quality of MSW compost is early source separation, perhaps requiring separation to occur before or at curbside collection.
In future, this trend may be attributed to economic and environmental factors, such as decrease in costs associated with landfilling and transportation of materials; adoption of legislation to protect the environment; decreasing commercial fertilizers use; increasing the capacity for household waste recycling and improved quality of compost products. It may be unwise to deem metals bound in the organic matter of MSW compost as unavailable for plant uptake. Therefore, sewage sludge should not be added to the compost at any point since it will raise the metal content of the compost. The physical and chemical makeup of MSW compost tends to shift with time and thus careful yearly monitoring of MSW compost quality is required.
This article is collectively written by Komal Naz 1, Muhammad Anwar-ul Haq 1, Zahoor Ahmad 2, and Muhammad Zia-ur-Rehman 1 from 1Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, and 2Department of Life Sciences, The Islamia University of Bahawalpur.