Anaerobic Digestion Method To Utilize Food Waste

Organic fraction of municipal solid waste (OFMSW) can be defined differently by regionally and nationally. For the United States of America, OFMSW is defined as a mixture of food, garden waste and paper. While for the European Union the OFMSW is known as a mixture of wastes from kitchens, gardens and parks. Besides that, production and composition of OFMSW also rely upon the number of inhabitants and their social condition, geographic region, the main economic activities, provincial food habits, season and recollection system.

The world overall municipal solid waste production is approximately 1300 million tons per year, and it is estimated that, in 2025, the amount of waste production will accelerate to 2200 million tons per year with approximately 46 % organic contents. During the past year, the used of anaerobic digestion on OFMSW and other organic waste has been used as a form to produced energy in the form of biogas (methane) and many researchers, companies and governmental agencies are actively working to improve the processes. To be compared with the process of incineration or landfilling, anaerobic digestion does not polluting the environment as the produced biogas is adequately used and the cost are more lower then aerobic treatment. Each year in the European Union, relatively 88 Million tons (Mt) of food is wasted and the environmental impacts of these losses throughout the food supply chain are widely recognized. While in South Korea, the amount of food wastes (FW) reproduce every one day elevated from 11,398 tons per day in 2003 to 13,697 tons per day in 2012, comparable to an increase from 22.5 to 29.1% of the municipal solid waste stream. FW in this research study covers both edible and inedible parts of food removed from the food supply chain excluding food use for bio-based process or for use as animal feed.

Generally, many countries agree that the management of food waste and livestock are one of the biggest challenge and they have been promptly taking action by source separated food waste treatment programs for the recovery of nutrients and bio energy, especially from restaurant. From the various types of organic wastes, FW have high organic content, which is a major portion (25-52.6%) of municipal solid wastes, which is suitable for biodegradation through anaerobic digestion (AD) approach for the production of renewable energy in the form of biogas.

Anaerobic digestion (AD) is defined as the process of waste management for the treatment of organic wastes such as sewage sludge and food waste that was used for the waste stabilization, methane generation and production of a digester that can be used as for agricultural purposed. While Li et. al. (2018) stated in their research paper that AD had already been practiced to reduce the volume of FW and to recover renewable energy such as methane from the FW. Researcher assured that the process of AD provides multiple environment benefits including the production of green energy, organic waste disposal and environment protection. The process of AD depends on a type of microorganism capability to break down biomass. AD consist of four main stages: hydrolysis, acidogenesis, acetogenesis methanogenesis. The production of methane from biomass which are the product of AD have more advantage compared to other renewable energy sources, which are the energy contained in it can be stored, transferred or convert into gaseous, liquid or solid fuels.

Based on the statistical analysis the Malaysian population had increased from 23.49 to 30.65 million between year 2000 until 2015. Therefore without doubt the generation of food waste will also increase throughout the years. This statement was proven by referring to a Municipal Solid Waste (MSW) study that was conducted with a result stated that 29,711 tonne/day waste was produced and 36,165 tonne/day MSW was estimated to produced by 2020. The waste that has been discarded or throw by people, residential houses, institutional building and also commercial building are known as Municipal Solid Waste (MSW). The increasing rate of MSW throughout the years thus producing problems to the nation. Thus, to dispose all the MSW, a method was practice in Malaysia which is by preparing open dumping area that producing yet another environmental threat towards the soil, water and air contamination.

Besides that the use of landfill throughout the years thus minimising the nation land area and maximizing the green house gases (GHG) emit from the landfill. The emission of GHG in the waste sector was estimated that it will emit around 54% from the year 1990-2008. However other than proposing a landfill area, some of the country prefer to overcome the problem by taking about 30 % to 40 % of the MSW to undergo process incineration and the balance MSW will undergo anaerobic digestion. The MSW that was stated in earlier paragraph that will be focused for this project is food waste. Generally food waste has the largest fraction in MSW for approximately 30%. Many definitions had been developed regarding the food waste.

Basically food waste is composed of carbohydrate polymers (starch, cellulose, hemicelluloses and lignin), lipid, protein and some other inorganic parts. Generally food waste can be classified into four groups which edible, non-edible and avoidable and unavoidable. In a study conducted in 2013, about 1.3 billion tons of food was produced but about one-third of it was lost along the food chain due to human consumption and approximately about 44% of urban food waste will be increase from year 2005 – 2025 according to Food and Agricultural Organization. Literally untreated food waste will cause threatening problems to its surrounding, for an example during its collection, transportation and storage that can cause contamination due to their characteristic as material that is easy to decompose. Consecutively, these problems have attracted the scientific community in working together to improve the situation.

Supporting this statement is the research conduct by Chen et al. (2017) where there are increase publication of treated food waste over the last few years. Hence to solve the threatening matter, a method to utilise the food waste is proposed which is anaerobic digestion. This method (Anaerobic Digestion) is a well known and proven its credibility used to utilize the organic waste by producing methane rich-biogas. Due to the well proven of this technology as a source of efficient energy producer it has been use to treat biodegradable waste, food waste, and organic fraction of municipal solid waste (OFMSW). Based on the research by Xiao et al. (2018), it is proven that anaerobic digestion is used in managing MSW by eliminating environmental threats produce at landfill to bring benefits such as producing renewable energy (methane and hydrogen), volatile fatty acid (VFA), alcohol and it is believe that this method is a low cost alternative. There are several definitions that best describe about the term anaerobic digestion. Anaerobic digestion is a naturally biochemical process that involving anaerobic bacteria in decomposing organic matter with the absence of oxygen. This term is further explained by believing that this process used several types of bacteria to utilize the organic waste to produce biogases which are methane and carbon dioxide. Anaerobic digestion is a worked process between a group of microorganism that depends on each other in decomposing substrate in four stages such as hydrolysis, acidegenosis, acetogenesis and methanogenesis.

11 February 2020
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