Trends in Food Waste Management

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 12.7 percent of the total municipal solid waste (MSW) generated in the year 2008 was food scraps that amounted to about 32 million tons. According to EPA, about 31 million tons of food waste was thrown away into landfills or incinerators in 2008. As far as United Kingdom is concerned, households throw away 8.3 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. Food waste can be recycled via:

  • In-vessel composting (IVC): 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.

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Vermicomposting

English: Freshly harvested worm castings Categ...

Vermicomposting is a type of composting in which certain species of earthworms are used to enhance the process of organic waste conversion and produce a better end-product. Vermicomposting is a mesophilic process utilizing microorganisms and earthworms. Earthworms feeds the organic waste materials and passes it through their digestive system and gives out in a granular form (cocoons) which is known as vermicompost. Like regular compost, vermicompost also benefits the environment by reducing the need for chemical fertilizers and decreasing the amount of waste going to landfills/dumpsites.

Vermicompost is primarily earthworm excrement, called castings, which can improve biological, chemical, and physical properties of the soil. The chemical secretions in the earthworm’s digestive tract help break down soil and organic matter, so the castings contain more nutrients that are immediately available to plants.

Earthworms consume various organic wastes and reduce the volume by 40–60 percent. Each earthworm weighs about 0.5 to 0.6 gram, eats waste equivalent to its body weight and produces cast equivalent to about 50 percent of the waste it consumes in a day. The moisture content of castings ranges between 32 and 66 percent and the pH is around 7.0. The worm castings contain higher percentage (almost twice) of both macro and micronutrients than the garden compost. About 2-3 kg of earthworms is required for 1000 kg of biomass, whereas about 1100 number earthworms are required for 1 m2 area.

There are nearly 3600 types of earthworms and they are mainly divided into two types: (1) burrowing; and (2) non-burrowing. Red earthworm species like Eisenia foetida and

Compost

 are most efficient in compost making. The non-burrowing earthworms eat 10 percent soil and 90 percent organic waste materials; these convert the organic waste into vermicompost faster than the burrowing earthworms. They can tolerate temperatures ranging from 0 to 40°C but the regeneration capacity is more at 25 to 30°C and 40–45% moisture level in the pile. The burrowing types of earthworms come onto the soil surface only at night. These make holes in the soil up to a depth of 3.5 m and produce 5.6 kg casts by ingesting 90 percent soil and 10 percent organic waste.

A wide range of agricultural residues, all dry wastes, for example, straw, husk, dry leaves of crops and trees, stalks, vegetable wastes, weeds etc can be converted into vermicompost. In addition, animal manures, dairy and poultry wastes, food industry wastes, municipal solid wastes, biogas sludge and bagasse from sugarcane factories also serve as good raw materials for vermicomposting.

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Composting Guidelines

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It seems everyone is concerned about the environment and trying to reduce their “carbon footprint”.  I hope this trend will continue and grow as a nationwide way to live and not turn into a fad.  Composting has been around for MANY years.  Composting is a great way to keep biodegradables out of the landfill and to reap the reward of some fabulous “black gold”.  That’s what master gardeners call compost and it’s great for improving your soil.  Plants love it.  Check out 10 Rules to Remember About Composting.

  1. Layer your compost bin with dry and fresh ingredients: The best way to start a compost pile is to make yourself a bin either with wood or chicken wire.  Layering fresh grass clippings and dried leaves is a great start.
  2. Remember to turn your compost pile: As the ingredients in your compost pile start to biodegrade they will start to get hot.  To avoid your compost pile rotting and stinking you need to turn the pile to aerate it.  This addition of air into the pile will speed up the decomposition.
  3. Add water to your compost pile: Adding water will also speed up the process of scraps turning into compost.  Don’t add too much water, but if you haven’t gotten any rain in a while it’s a good idea to add some water to the pile just to encourage it along.
  4. Don’t add meat scraps to your pile: Vegetable scraps are okay to add to your compost pile, but don’t add meat scraps.  Not only do they stink as they rot, but they will attract unwanted guests like raccoons that will get into your compost bin and make a mess of it.
  5. If possible have more than one pile going: Since it takes time for raw materials to turn into compost you may want to have multiple piles going at the same time.  Once you fill up the first bin start a second one and so on.  That way you can allow the ingredient in the first pile to completely transform into compost and still have a place to keep putting your new scraps and clippings.  This also allows you to always keep a supply of compost coming for different planting seasons.
  6. Never put trash in your compost pile: Just because something says that it is recyclable it doesn’t mean that it should necessarily go into the compost bin.  For example, newspapers will compost and can be put into a compost pile, but you will want to shred the newspapers and not just toss them in the bin in a stack.  Things like plastic and tin should not be put into a compost pile, but can be recycled in other ways.
  7. Allow your compost to complete the composting process before using: It might be tempting to use your new compost in your beds as soon as it starts looking like black soil, but you need to make sure that it’s completely done composting otherwise you could be adding weed seeds into your beds and you will not be happy with the extra weeds that will pop up.
  8. Straw can be added if dried leaves are not available: Dried materials as well as green materials need to be added to a compost bin.  In the Fall you will have a huge supply of dried leaves, but what do you do if you don’t have any dried leaves?  Add straw or hay to the compost bin, but again these will often contain weed seeds so be careful to make sure they are completely composted before using them.
  9. Egg Shells and Coffee grounds are a great addition: Not only potato skins are considered kitchen scraps.  Eggshells and coffee grounds are great additions to compost piles because they add nutrients that will enhance the quality of the end product.
  10. Never put pet droppings in your compost pile: I’m sure you’ve heard that manure is great for your garden, but cow manure is cured for quite a while before used in a garden.  Pet droppings are far to hot and acidic for a home compost pile and will just make it stink.

Contributed by Roxanne Porter whose original blogpost can be viewed at http://www.nannypro.com/blog/10-rules-to-remember-about-composting/

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Utilization of Biogas and Digestate

An anaerobic digestion plant produces two outputs, biogas and digestate; both can be further processed or utilized to produce secondary outputs. Biogas can be used for producing electricity and heat, as a natural gas substitute and also a transportation fuel. A combined heat and power plant system (CHP) not only generates power but also produces heat for in-house requirements to maintain desired temperature level in the digester during cold season. CHP systems cover a range of technologies but indicative energy outputs per m3 of biogas are approximately 1.7 kWh electricity and 2.5kWh heat. The combined production of electricity and heat is highly desirable because it displaces non-renewable energy demand elsewhere and therefore reduces the amount of carbon dioxide released into the atmosphere.

In Sweden, compressed biogas is used as a transportation fuel for cars and buses. Biogas can also be upgraded and used in gas supply networks. The use of biogas in solid oxide fuel cells is being researched.

The surplus heat energy generated may be utilized through a district heating network. Thus, there is potential scope for biogas facilities in the proximity of new housing and development areas, particularly if the waste management system could utilise kitchen and green waste from the housing as a supplement to other feed stock.

Digestate can be further processed to produce liquor and a fibrous material. The fiber, which can be processed into compost, is a bulky material with low levels of nutrients and can be used as a soil conditioner or a low level fertilizer. A high proportion of the nutrients remain in the liquor, which can be used as a liquid fertilizer.