Introduction
The problem of waste management runs across geographies and its gravest causal agent, i.e., urbanism, is a global phenomenon. However, its ramifications are relatively more pronounced in developing nations on account of improved standards of living and changing consumption patterns. The growing population and increasing consumer demand are leading to excessive consumption of available resources and generation of tremendous amount of different kind of wastes, which is emerging as a chronic problem in urban societies. Their efficient management is needed at the earliest to avoid numerous problems related to public and environmental health.
The waste management hierarchy suggests that Reduce, Reuse and Recycling should always be given preference in a typical waste management system. However, these options cannot be applied uniformly for all kinds of wastes. For example, organic waste is quite difficult to deal with using the conventional 3R strategy. Of the different types of organic wastes available, food waste holds the highest potential in terms of economic exploitation as it contains high amount of carbon and can be efficiently converted into biogas and organic fertilizer.
Market Size
A consistent growth rate of 8 to 10 percent for India is symbolic of its increasing production and consumption trends. The main reasons for such trends have been the increasing disposable incomes and the growing consumerism and urbanism. All this has significantly contributed to the growth and economic development of the country, apart from tremendous increase in waste generation across the country.
The amount of waste generated by any country is directly proportional to its population and the mean living standards of the people. As per the last census of India, the Indian population was 1027 million with about 5161 urban cities and towns contributing up to 28% of the total population. A constant rate of increase of about 30% per decade in the number of town/cities urbanized is something to be considered with utmost diligence, since it is the urban areas which mostly contribute to the waste generation. The situation grows even starker from the observation that the per capita waste generation in India has been rising by about 1.0-1.3% annually over the past few decades and the population itself has been rising at an annual rate of 1.2-1.5%.
With organic or food waste being one of the main constituent of the total urban waste generated, it not only makes it essential to seek means for its safe disposal, but at the same time, reiterates the huge business potential that ensues the proper utilization of such a widely available potential energy/power resource.
Anaerobic Digestion Technology
Anaerobic digestion is a proven and commercially available technology to handle wastes having high carbon content. It is widely acknowledged as the best means to deal with organic waste in rural as well as urban areas. One of the major benefits of anaerobic digestion is its having almost no impact on the environment, since it saves on emissions which would have been caused if the organic waste was dumped into landfills instead or an equivalent amount of power would be generated using conventional fossil-fuel based resources.
Another important feature is its scalability and ability to accept varied types of biomass. World over, the technology has been reaching newer and higher scales, with plants of capacity 300 tonnes per day and above already in operation in countries like Germany, Sweden and Italy.
Process Description
The feedstock to be utilized, e.g., organic waste from various sources, is first collected and then passed through a shredder to reduce the minimum particle size. The homogenated mass is then moved to a mixing tank, wherein it is mixed with the recirculated digestate to bring it in contact with some of the worn out/used microbial biomass to increase the rate of biochemical degradation in the subsequent steps and also to make the input feed more acclimatized to the system or process requirements. This homogenate, along with the recirculated digestate from the mixing tank, which is responsible for maintaining the adequate solid content in the feed in terms of volume, is then transferred to a storage tank.
