Tag Archives: Composting

An Introduction to Composting

  By Salman Zafar | April 10, 2013 - 6:43 am | Composting, Waste Management
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The composting process is a complex interaction between organic waste and microorganisms. The microorganisms that carry out this process fall into three groups: bacteria, fungi, and actinomycetes. Actinomycetes are a form of fungi-like bacteria that break down organic matter. The first stage of the biological activity is the consumption of easily available sugars by bacteria, which causes a fast rise in temperature. The second stage involves bacteria and actinomycetes that cause cellulose breakdown. The last stage is concerned with the breakdown of the tougher lignins by fungi.

Central solutions are exemplified by low-cost composting without forced aeration, and technologically more advanced systems with forced aeration and temperature feedback. Central composting plants are capable of handling more than 100,000 tons of biodegradable waste per year, but typically the plant size is about 10,000 to 30,000 tons per year. Biodegradable wastes must be separated prior to composting: Only pure foodwaste, garden waste, wood chips, and to some extent paper are suitable for producing good-quality compost.

Composting Equipment

The composting plants consist of some or all of the following technical units: bag openers, magnetic and/or ballistic separators, screeners (sieves), shredders, mixing and homogenization equipment, turning equipment, irrigation systems, aeration systems, draining systems, bio-filters, scrubbers, control systems, and steering systems. The composting process occurs when biodegradable waste is piled together with a structure allowing for oxygen diffusion and with a dry matter content suiting microbial growth.

Biodegradable wastes must be separated prior to composting: Only pure food waste, garden waste, wood chips, and to some extent paper are suitable for producing good-quality compost.The temperature of the biomass increases due to the microbial activity and the insulation properties of the piled material. The temperature often reaches 65 to 75 degrees C within few days and then declines slowly. This high temperature hastens the elimination of pathogens and weed seeds.

Composting Methodologies

The methodology of composting can be categorized into three major segments—anaerobic composting, aerobic composting, and vermicomposting. In anaerobic composting, the organic matter is decomposed in the absence of air. Organic matter may be collected in pits and covered with a thick layer of soil and left undisturbed six to eight months. The compost so formed may not be completely converted and may include aggregated masses.

Aerobic composting is the process by which organic wastes are converted into compost or manure in presence of air and can be of different types. The most common is the Heap Method, where organic matter needs to be divided into three different types and to be placed in a heap one over the other, covered by a thin layer of soil or dry leaves. This heap needs to be mixed every week, and it takes about three weeks for conversion to take place. The process is same in the Pit Method, but carried out specially constructed pits. Mixing has to be done every 15 days, and there is no fixed time in which the compost may be ready.

Berkley Method uses a labor-intensive technique and has precise requirements of the material to be composted. Easily biodegradable materials, such as grass, vegetable matter, etc., are mixed with animal matter in the ratio of 2:1. Compost is usually ready in 15 days.

Vermicomposting involves use of earthworms as natural and versatile bioreactors for the process of conversion. It is carried out in specially designed pits where earthworm culture also needs to be done. Vermicomposting is a precision-based option and requires overseeing of work by an expert. It is also a more expensive option (O&M costs especially are high).

Waste Management Outlook for India

  By Ranjith Annepu | March 13, 2013 - 9:03 am | India, Solid Waste Management
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Waste management crisis in India should be approached holistically; while planning for long term solutions, focus on addressing the immediate problems should be maintained. National and local governments should work with their partners to promote source separation, achieve higher percentages of recycling and produce high quality compost from organics. While this is being achieved and recycling is increased, provisions should be made to handle the non-recyclable wastes that are being generated and will continue to be generated in the future.

Recycling, composting and waste-to-energy are all integral parts of the waste disposal solution and they are complementary to each other; none of them can solve India’s waste crisis alone. Any technology should be considered as a means to address public priorities, but not as an end goal in itself. Finally, discussion on waste management should consider what technology can be used, to what extent in solving the bigger problem and within what timeframe.

Experts believe India will have more than nine waste-to-energy projects in different cities across India in the next three years, which will help alleviate the situation to a great extent. However, since waste-to-energy projects are designed to replace landfills, they also tend to displace informal settlements on the landfills. Here, governments should welcome discussions with local communities and harbor the informal recycling community by integrating it into the overall waste management system to make sure they do not lose their rights for the rest of the city’s residents.

This is important from a utilitarian perspective too, because in case of emergency situations like those in Bengaluru, Kerala, and elsewhere, the informal recycling community might be the only existing tool to mitigate damage due to improper waste management as opposed to infrastructure projects which take more than one year for completion and public awareness programs which take decades to show significant results.

Involvement of informal recycling community is vital for the success of any SWM program in India

Indian policy makers and municipal officials should utilize this opportunity, created by improper waste management examples across India, to make adjustments to the existing MSW Rules 2000, and design a concrete national policy based on public needs and backed by science. If this chance passes without a strong national framework to improve waste management, the conditions in today’s Bengaluru, Thiruvananthapuram, Kolkata, Mumbai, Chennai, Coimbatore and Srinagar will arise in many more cities as various forcing factors converge. This is what will lead to a solid waste management crisis affecting large populations of urban Indians.

The Indian Judiciary proved to be the most effective platform for the public to influence government action. The majority of local and national government activity towards improving municipal solid waste management is the result of direct public action, funneled through High Courts in each state, and the Supreme Court. In a recent case (Nov 2012), a slew of PILs led the High Court of Karnataka to threaten to supersede its state capital Bengaluru’s elected municipal council, and its dissolution, if it hinders efforts to improve waste management in the city. In another case in the state of Haryana, two senior officials in its urban development board faced prosecution in its High Court for dumping waste illegally near suburbs. India’s strong and independent judiciary is expected to play an increasing role in waste management in the future, but it cannot bring about the required change without the aid of a comprehensive national policy.

Note: Acknowledgements will be published in the full report “Observations from India’s Crisis” on wtert.org and blog.wtert.org

Food Waste Management

  By Salman Zafar | February 21, 2013 - 12:41 am | Biogas, Waste Management
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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 examples, 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.

There are numerous places which are the sources of large amounts of food waste and hence a proper food-waste management strategy needs to be devised for them to make sure that either they are disposed off in a safe manner or utilized efficiently. These places include hotels, restaurants, malls, residential societies, college/school/office canteens, religious mass cooking places, airline caterers, food and meat processing industries and vegetable markets which generate organic waste of considerable quantum on a daily basis.

The anaerobic digestion technology is highly apt in dealing with the chronic problem of organic waste management in urban societies. Although the technology is commercially viable in the longer run, the high initial capital cost is a major hurdle towards its proliferation.

The onus is on the governments to create awareness and promote such technologies in a sustainable manner. At the same time, entrepreneurs, non-governmental organizations and environmental agencies should also take inspiration from successful food waste-to-energy projects in Western countries and try to set up such facilities in cities and towns.

Food Waste Management in USA

  By Salman Zafar | February 10, 2013 - 11:37 pm | Anaerobic Digestion, Waste Management, Waste-to-energy
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Food waste is an untapped energy source that mostly ends up rotting in landfills, thereby releasing greenhouse gases into the atmosphere. Food waste is difficult to treat or recycle since it contains high levels of sodium salt and moisture, and is mixed with other waste during collection. Major generators of food wastes include hotels, restaurants, supermarkets, residential blocks, cafeterias, airline caterers, food processing industries, etc.

In United States, food waste is the third largest waste stream after paper and yard waste. Around 13 percent of the total municipal solid waste generated in the country is contributed by food scraps. According to USEPA, about 34 million tons of food waste was thrown away into landfills or incinerators in 2010. As far as United Kingdom is concerned, households throw away around 8 million tons of food each year. These statistics are an indication of tremendous amount of food waste generated all over the world.

The proportion of food waste in municipal waste stream is gradually increasing and hence a proper food waste management strategy needs to be devised to ensure its eco-friendly and sustainable disposal. The two most common methods for food waste recycling are:

  • Composting: A treatment that breaks down biodegradable waste by naturally occurring micro-organisms with oxygen, in an enclosed vessel or tunnel;
  • Anaerobic digestion (AD): A treatment that breaks down biodegradable waste in the absence of oxygen, producing a renewable energy (biogas) that can be used to generate electricity and heat.

Currently, only about 3 percent of food waste is recycled throughout U.S., mainly through composting. Composting provides an alternative to landfill disposal of food waste, however it requires large areas of land, produces volatile organic compounds and consumes energy. Consequently, there is an urgent need to explore better recycling alternatives. Anaerobic digestion has been successfully used in several European and Asian countries to stabilize food wastes, and to provide beneficial end-products. Sweden, Austria, Denmark, Germany and England have led the way in developing new advanced biogas technologies and setting up new projects for conversion of food waste into energy.

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. Food waste can either be used as a single substrate in a biogas plant, or can be co-digested with organic wastes like cow manure, poultry litter, sewage, crop residues, abattoir wastes, etc.

Food waste is one of the single largest constituent of municipal solid waste stream.  Diversion of food waste from landfills can provide significant contribution towards climate change mitigation, apart from generating revenues and creating employment opportunities. Rising energy prices and increasing environmental pollution makes it more important to harness renewable energy from food wastes. Anaerobic digestion technology is widely available worldwide and successful projects are already in place in several European as well as Asian countries which makes it imperative on waste generators and environmental agencies in USA to strive for a sustainable food waste management system.

Different Strategies in Composting

  By Salman Zafar | February 6, 2013 - 11:11 pm | Composting, Waste Management
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The methodology of composting can be categorized into three major segments—anaerobic composting, aerobic composting, and vermicomposting. In anaerobic composting, the organic matter is decomposed in the absence of air. Organic matter may be collected in pits and covered with a thick layer of soil and left undisturbed six to eight months. The compost so formed may not be completely converted and may include aggregated masses.

Aerobic composting is the process by which organic wastes are converted into compost or manure in presence of air and can be of different types. The most common is the Heap Method, where organic matter needs to be divided into three different types and to be placed in a heap one over the other, covered by a thin layer of soil or dry leaves. This heap needs to be mixed every week, and it takes about three weeks for conversion to take place. The process is same in the Pit Method, but carried out specially constructed pits. Mixing has to be done every 15 days, and there is no fixed time in which the compost may be ready. Berkley Method uses a labor-intensive technique and has precise requirements of the material to be composted. Easily biodegradable materials, such as grass, vegetable matter, etc., are mixed with animal matter in the ratio of 2:1. Compost is usually ready in 15 days. When transferring compost, be sure to use the safest, tear-resistant compostable plastic bags available in the market.

Vermicomposting involves use of earthworms as natural and versatile bioreactors for the process of conversion. It is carried out in specially designed pits where earthworm culture also needs to be done. Vermicomposting is a precision-based option and requires overseeing of work by an expert. It is also a more expensive option (O&M costs especially are high). However, unlike the above two options, it is a completely odorless process making it a preferred solution in residential areas. It also has an extremely high rate of conversion, so quality of the end product is very high with rich macro and micronutrients. The end product also has the advantage that it can be dried and stored safely for a longer period of time.