A food waste composting

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1. Introduction

The aim of the research study is to make an overall analysis of food wastes, its various types and their causes, composting and different processes involved, various methods and techniques practiced in different countries, and overall benefits and advantages/disadvantages of food waste composting. There are mainly two broad categories of food waste viz., organic food waste arising due to human consumption at home, restaurants and inorganic waste which occurs at upstream and downstream levels involved in food manufacturing process etc. Food waste are categorized in to various types namely production, processing, distribution, acquisition, preparation, and consumption

The evil consequences of food waste are due to large amount of energy losses occur when food is dispensed, comprising the energy needed for production and distribution of food, processing wasted food, as well as the energy seized inside the food itself. However certain types of food waste are unavoidable and hence composting process is adopted to marginalise evil aspects of the former. Composting is a process carried out under controlled biological maturity at aerobic conditions, where organic matter of animal or vegetal origin is decomposed to materials with shorter molecular chains, more stable, hygienic, humus rich, and finally beneficial for the agricultural crops and for recycling of soil organic matter. Compost helps to return organic materials to the soil and keeps them out of landfills and waterway and overall can also be used as a mulch, a liquid “fertilizer,” or integrated into the soil. The agents of composting are divided in to primary, secondary, and tertiary level of consuments.

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Ideally there are 2 phases of composting in which organic matter undergo change known as Degradation and Maturation. Various methods of composting for home, agricultural or industrial etc with specific mention to latest methods like NADEP are clearly highlighted for better understanding with the multiple parameters involved in composting process also being given adequate attention. The research study categorized the best composting practices adopted in various countries and gives cue in selecting most economically viable ones in current use with their benefits.

1.1 Research Overview

Objective

The objective of the project is to make an overall study of the food waste, its various types and their causes, composting and different processes involved, various methods and techniques practiced in different countries, and overall benefits and advantages/disadvantages of food waste composting.

Scope

The scope of this project is to describe the different method/techniques used for food waste composting and study various processes and different parameters involved with special mention to the composting practiced in different countries.

Schedule

The Schedule of this project is as follows

  • Initial brief of the project due on August 28th, 2009, which will cover the Title, Objective, Scope and Schedule.
  • Interim Report on September 25th, 2009, covering the Title, Objective, Scope, Proposed Table of contents and literature review.
  • Final Report on the November 13th, 2009, covering the detailed description on Abstract, Introduction/ literature review, Materials and Methods, Results, Discussion, Acknowledgements, References

Time Frame

The project will be initiated and executed from August 28th, 2009 until November 13th, 2009.

Project Planning

The project planning has been done according to “Independent Study” course timetable. For the completion of this project a 13 week time frame was available

2. Food Waste - A Brief Description

2.1 Definition

Food waste is defined as all food produced or purchased that is discarded by humans [1]. Food waste normally occurs at various levels of food system stages or supply chain namely production, processing, apportionment, procurement, preparation and finally consumption [2].

Various types of Food waste can be described as below:

2.2.1 Production food wastes:

They usually take place due to destruction caused by predator or insects or from natural disaster, ill managed government programs encouraging farmers to produce certain foods in excess, [3],[4] farmers aligning to selective harvesting, or inability to harvest anything as a result of bad crop yields or reduced market rates [5]. Different kinds of food waste also occur at the farms during storage caused either by pest or food decay.

2.2.2 Processing food wastes:

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Food processing wastes prime contributing factors include ineffectual processing methods for removal of edible and inedible parts of food and spillage. Also in developed western counties large portion of processing wastes are accounted for in the inedible parts of food namely bones, skins, eyes, peels, blood and other low quality miniscule products [6].

In practice, the wastes generated from food processing industry have the below indicated distinct qualities:

  1. Higher amount of proteins, carbohydrates, and lipids.
  2. Distinct quantity of suspended solids largely dependent on the source
  3. High amount of chemical or biochemical oxygen demand.

2.2.3 Distribution food waste

These food waste categories are due to inefficient handling of food, during food packing, conveyance, overstocking of certain food stocks, and improper stock cycle. Also larger portion of food service waste arises due to plate leftovers, significant food service waste comes from plate scraps, which in some countries are not retrieved due to food safety because of food safety criteria's and larger food portion sizes

2.2.4 Consumer food waste

They occur during food acquisition, preparation, and consumption. Improper or extended storage is a pivotal cause of consumer food waste. During preparation, consumers may try to remove inedible or defective portions of foods along with edible portions such as skins to obtain desired sensory or nutritional qualities. Remnant foods may be fed to pets, decreasing the amount of unutilized food but also reducing availability of foods for humans. The availability of cheap food, particularly in industrialized nations, encourages buying in excess and stock pile habits that result in waste [7].

Various types of vegetables, fruits, coffee filters, eggshells, newspaper, meat, food grains, bread, dairy produce etc can be composted. Food waste has distinctive properties as a raw compost agent. Also as they have increased moisture contents and reduced physical structure, it becomes imperative to blend fresh food waste with a bulking agent that will absorb part of surplus moisture and in turn augment structure to the mixture. Typically sawdust, yard waste are preferred choices of bulking agents due to their high C: N ratio.

2.2 Effects of food waste

Food waste has dire consequences on the environment surrounding us and community health [8]. Large amount of energy losses occur when food is dispensed, comprising the energy needed for production and distribution of food, processing wasted food, as well as the energy seized inside the food itself.

Wasted food threatens environmental and community health through destruction of the biophysical environment, air pollution from decaying food, water pollution from runoff or leaching, and rapidly growing landfills.

Amid popular thoughts, it has been proved that organic wastes do not decay or evaporate in landfills, owing to the anaerobic environment in which the waste is buried [9]. From an ecological point of view, minimizing food waste encourages environmental sustainability by conserving energy sources, decreasing environmental costs towards burning fossil fuels, shielding microhabitats, and conserving air and water quality. Also from nutritional viewpoint, there would be increase in the availability of nutrients due to reduction in food waste, and improved community health and community food security [10].

3. Composting: An overview

Composting is a process carried out under controlled biological maturity at aerobic conditions, where organic matter of animal or vegetal origin is decomposed to materials with shorter molecular chains, more stable, hygienic, humus rich, and finally beneficial for the agricultural crops and for recycling of soil organic matter[11].

The process is controlled by various microorganisms inhabiting in aerobic conditions like bacteria, actinomycetes, fungi, algae and protozoa, which partake typically in the organic biomass or schmaltzy added [12].

The composting process can be detailed in the below equation:

Organic Matter + O2  Compost + CO2 + H20 + NO3- + SO24- + Heat

The focal point of interest in the process of composting are aimed at following key points

  1. Environmental
  2. During the composting process there occurs the transmutation of biomass into material affluent nutritional substances which can improve the structural physiognomy of the [13].

  3. Hygienic
  4. During the composting process under the effect of high temperature the organic matter is largely disinfected [14].

  5. Energy management
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During the composting process energy is released through the degradation of large organic molecules [15].

Compost typically tends to provide numerous advantages to the landscape and garden.

Also compost helps to return organic materials to the soil and keeps them out of landfills and waterway and overall can also be used as a mulch, a liquid “fertilizer,” or integrated into the soil [16]

3.1 Agents for Composting

The inter-relationships between various components of the compost pile is intricate and could be diagrammatically shown by one pyramid of primary, secondary, and tertiary level consuments[16]

The base of the pyramid is made up of organic matter including plant and animal residues.

The organic residues, such as leaves or other plant materials, are eaten by some types of invertebrates, like millipedes, sow bugs, snails, and slugs. These invertebrates shred the plant materials, creating more surface area for action of fungi, bacteria, and actinomycetes, which are in turn eaten by organisms such as mites and springtails. Many kinds of worms, including earthworms, nematodes, red worms, and pot worms, eat decaying vegetation and microbes and excrete organic compounds that enrich compost. There tunnels aerate the compost and their feeding increases the surface of organic matter for microbes to act upon.

As each decomposer dies or excretes, more food is added to the system for other decomposers.

3.2 Process of Composting

In composting process occurring in the presence of oxygen, the microorganisms (bacteria, fungi, actinomycetes) and invertebrates (worms, millipedes, sow bugs) that decompose food wastes require oxygen and water. Products of the composting process include compost, carbon dioxide, heat and water. The heat produced increases the temperature in the compost pile to as high as 160°F. This increased temperature results in increased water evaporation. As the process nears completion (1 month to 2 years), the pile temperature lowers. The conversion of carbon (C) in waste to carbon dioxide results in reduction in weight and volume of the pile. Nitrogen (N) in food waste is necessary for microorganisms to carry out decomposition effectively. Finished compost takes on many of the characteristics of humus

3.3 Micro organisms in Composting

Microorganisms such as bacteria, fungi and actinomycetes account for most of the decomposition, as well as the rise in temperature that occurs in the composting process.

Tiny millipedes, insects, sowbugs and earthworms are primary agents of physical decay. They break up waste debris and transport microorganisms. The speed at which organic materials decompose depends on the decomposers, type of organic materials and composting method used. The food web of the compost pile shows the relationships in the process

3.4 Phases of Composting

there are two phases in composting in which organic matter undergoes changes. They include

  1. Degradation and
  2. Maturation

The first phase of the composting process starts with the degradation of the most easily degrading organics (sugars, organic acids, amino acids). It is mediated by aerobic microorganisms with consumption of oxygen and release of carbon dioxide and energy. This is a thermophilic phase, which proceeds with high velocity; its duration is between several weeks and a few months, depending of the substrate characteristics. The vigorous aeration or mixing

of the composting components is an obligatory condition to ensure the cooling of the substrate, but also to support the oxygen supply to biomass. Phytotoxins are produced during this phase of the process, which proceeds by the decomposition of the organics [17].

The high temperatures, pH conditions, and humidity are the reasons that the most active microorganisms during this phase are the bacteria. In the end of the first phase fresh compost is obtained. When the easily degradable compounds that are metabolized during the first stage are exhausted, the composting process continues with the more complex organic molecules; that is why the time for degradation is longer.

The beginning of this stage is followed by the death of a huge part of microbial population, because of lack of available food. Additionally, the fast decrease of temperature is followed by changes in the population of active microorganisms from thermophilic to mesophilic. It is true that during this stage the temperature reaches 40-458C to decrease until room temperature.

This current would last few months and during the mesophilic phase actinomycetes appear. They degrade actively the starch, cellulose, and lignin compounds necessary for the synthesis of humus components. They play also a basic role in the humus formation and produce aromatic compounds, which give to the end product a specific smell of wood soil [18]

The maturation stage is characterized also with disintegration of the compost material: formation of small particles by a lot of invertebrates (earthworms, ticks, and centipede). The humus formation is strongly related to chemical and biological transformation of animal and vegetable wastes and with microbial synthesis. The humufication is attributed to oxidative

polymerization of phenolics obtained by the catabolism of lignin, tannins, and polyphenols, or to new microbial biosynthesis.

4. Method/Techniques of Food Waste Composting

4.1. NADEP Technique

NADEP is the modified technique of composting. For making compost, wide range of organic materials is used such as crop residues, weeds and kitchen waste.

To set up this method to make compost, a perforated rectangular brick tank of about 10' x 6' x 3' needs to be constructed. The tank is filled up with layers of agricultural wastes and food scrap, dung and soil one above the other till the tank is full. The ground should be made compact with slurry of dung to reduce seepage. Following are the raw material required to fill the tank to get a good quality of compost [19]

  • Agricultural waste (Dry & green) - 1350-1400 kgs.
  • Cattle dung or biogas slurry - 98 - 100 kgs.
  • fine sieved soil - 1675 kgs.

Water - 1350-1400 litres and Fill the bottom 15 cm with organic waste.

The entire tank should be filled in one go, within 24 hours and should not go beyond 48 hours, as this would affect the quality of the compost.

Slurry of cow dung by mixing 4 kg of dung in about 150 liters of water is prepared and uniformly apply it over the first layer. Over this, spread evenly about 50-60 kg of soil. Sprinkle water so that the soil settles down. This sequence can be repeated several times to fill the tank in 12-14 layers. The top of the tank is then plastered with 7.5 cm thick layer of clay soil mixed with dung to facilitate bacterial activity from all four sides. Sprinkle water to keep the unit moist. Within 100-120 days the compost is ready for harvest [19].

Benefits:

  • Reduced cash expenses on chemical fertilizer, improved soil fertility, increased crop yield
  • Supports organic crop production, reduced dependence on outside inputs
  • Each NADEP tank produced approximately 2.5 tons of compost and is prepared within 90-120 days.

4.2 Pit Composting

This method involves making compost in pits which have been dug in the ground. The depth for a pit varies according to local soil conditions and the depth of the water table. A typical pit measures about 1.5 to 2m wide, 50cm deep and any length. To reduce water loss, the pit is lined with a thin layer of clay. Several trenches are dug next to each other, to allow turning from one pit into the next. The pits should not be dig close to each other as the walls between them will be thin and may collapse[20].

The layering is as follows:

  1. 10cm of material which is difficult to decompose (stalks or crop residues)
  2. 10cm of material which is easy to decompose (fruit and vegetable scraps)
  3. 2cm of animal manure (if available)
  4. A thin layer of soil from the surface of cropped land to obtain the microorganisms needed for the composting process
  5. Repeat these layers until the heap reaches 1 to 1.5m high
  6. Cover with grass or leaves to prevent water loss

After 2 to 3 weeks, all the contents of the pit should be turned over into the second pit and 2 to 3 weeks later this should be turned into the third pit. As the decomposing material from pit 1 is

turned into pit 2, new material which is ready for composting can be put into pit 1, thus creating a process of continual compost making [21].

Advantages:

  • Pit composting is easy, quick and cheap as it does not require investment in materials.
  • Require less water so it is useful for dry areas.
  • Disadvantages:

  • Require hard work to dig the pits especially if labour is limited.

4.3 Composting method for homes

Composting kitchen Food scraps is one of the best and easiest things to reduce waste and grow a healthy, sustainable garden. Using compost in garden recycles nutrients and organic matter that help grow trouble-free plants with less water, fertilizer or pesticides.

Compost also builds healthy soil that absorbs and filters runoff, protecting streams from erosion and pollution. However, they are also attractive to disease-carrying pests like rats, and must be composted with care. Meat, fish, poultry, dairy products and pet wastes should not be composted in any system at home-they break down slowly, create bad odors and attract pests.

Items to be put inside Food scrap compost system can be illustrated as follows:

Bury in garden, compost in worm bins or food digesters
Greens: fruit and vegetable trimmings, bread and grains, coffee
grounds and filters, tea bags, fruit from yard, Eggshells

Browns: (bedding): newspaper, cardboard, fall leaves, clean sawdust or shavings
Do not compost or bury
Meat, fish, poultry or dairy products-put in disposal or trash.

Pet wastes-flush down the toilet, or bag in plastic and put in trash.

Evergreen leaves, sawdust or shavings from painted or treated wood, coated paper.

Table 2: Different food products for home compost

There are three simple and reliable ways to compost food scraps without pests:

  • Burying food scraps in the garden is a simple method requiring no special tools.
  • Food “digesters” provide a convenient and pest resistant way to compost food scraps.
  • Worm bins is a method for composting food scraps to produce rich compost.

4.3.1 Burying Food Scraps in the Garden

Burying food wastes in the garden is a safe and easy way to compost. Garden soil provides a natural barrier that keeps out flies and other pests, and holds in moisture and odors.

Food scraps can be buried in empty areas of vegetable and flower gardens, or below the ends of branches of trees and shrubs. shovel or post hole digger is used to dig a hole 2 to 3 inches of food scraps is added to the hole and it is mix well and covered with soil to keep pest check for signs of digging by rodents, dogs or other pests. If you see signs of digging, it may be better to switch to a digester or worm bin that excludes pests.

Food scraps may take from 1 to 6 months to decompose depending on the season, moisture, soil and what is buried. Seeds and small seedlings may be planted on top of buried food scraps immediately. Large transplants should not be planted

4.2.1 Food Digesters

Food digester is an air tight, oxygen-free container that is fed with a food scraps. A biological process occurs to this mixture to produce methane gas, commonly known as biogas, along with an odor-reduced effluent. Microbes break down manure into biogas and a nutrient-rich effluent.

Digesters provide more protection from pests than garden burial, and require less work than digging holes for burial or maintaining a worm bin. Digesters can be fed for 6 to 12 months before they are full of food scraps.

4.3.2 Worm Bin

Worm composting is a method for recycling food waste into a rich, dark, earth-smelling soil conditioner. The great advantage of worm composting is that this can be done indoors and

Outdoors. It also provides apartment dwellers with a means of composting. In a nutshell, worm compost is made in a container filled with moistened bedding and red worms. Add food waste for a period of time, and the worms and micro-organisms will eventually convert the entire contents into rich compost [22].

5. Different Parameters in Composting

The various parameters which are involved in the composting processes can be enumerated as below:

5.1 Temperature

Temperature is directly proportional to the biological activity within the composting system. Composting will take place within two temperature ranges known as mesophilic (50-105F) and thermophilic (over 105F). The initial decomposition is carried out by mesophilic microorganisms, which rapidly break down the biodegradable compounds. The heat produced by them causes the fast increase of compost temperature. Although mesophilic temperatures allow effective composting, experts suggest maintaining temperatures between 110 and 150. The thermophilic temperatures are desirable because they destroy more pathogens, weed seeds and fly larvae in the composting materials proteins, fats, and complex. When these compounds are exhausted, the compost temperature gradually decreases and mesophilic microorganisms once again take part for the final phase of “curing” or maturation of the remaining organic matter[16].

Temperatures greater than 140°F reduce the activity of most organisms. A temperature probe or soil thermometer can be used to keep track of compost temperatures.

5.2 C/N Ratio

Carbon (C), nitrogen (N), phosphorous (P), and potassium (K) are the primary nutrients required by the microorganisms involved in composting. Carbon provides an energy source and the building material representing 50% of the microbial cell biomass. Nitrogen is a critical component of the proteins, nucleic acids, enzymes, and coenzymes necessary for cell growth and function.

5.2.1 Oxygen & pH

The oxygen is also an essential ingredient for successful composting because it is an aerobic process. Although the atmosphere contains 21% oxygen, the aerobic microbes can survive at concentrations as low as 5%. In this sense a content of 10% of oxygen is considered optimal for the composting.[23]

On the other hand, a pH between 5.5 and 8.5 is optimal for compost microorganisms.

When the bacteria and fungi digest organic matter, they release organic acids. As the pH decreases, the growth of fungi increases, followed by decomposition of lignin and cellulose. If the system becomes anaerobic, the acid accumulation can lower the pH to 4.5, thus limiting the microbial activity. In such cases, the introduction of air is usually sufficient to return the compost pH to acceptable

5.2.2 Humidity

Water is a fundamental life factor of active compost microorganisms, because:

  • It is necessary for the nutrients exchange via cell membranes.
  • It is a transport environment for the extracellular enzymes and soluble substrates.

Composting materials should be maintained within a range of 40% to 65% moisture [23]

6. Food Waste Composting- Overview in Different Countries

6.1 USA

According to the U.S.Department of Agriculture Economic Research Service, if 5% of consumer, retail, and food service food discards from 1995 were recovered, savings from landfill costs alone would be about $50 million dollars annually. Recovering 5% of losses from these three sources “would represent the equivalent of a day's food for each of 4 million people.” Food discards comprise 6.7% by weight of the total U.S. municipal solid waste stream. In 1995, 14,000,000 tons of food discards were generated. Of this, only 4.1%, 600,000 tons, was diverted, or recovered, from the traditional disposal destinations of landfills and incinerators. Almost any business can successfully create fewer discards by buying less, and can divert food discards from landfills. Businesses with record-setting food diversion programs are recovering 50 to 100% of their food discards and reducing their overall solid waste by 33 to 85% [24].

Often, recovery of food and other organics is just one part of a successful overall waste reduction program that realizes both environmental and economic benefits.

These kinds of programmes allow one to:

  • Avoid trash collection and disposal fees;
  • Provide food to the needy;
  • Recover the nutrient value of the food as compost or animal food;
  • Help your community meet local and state waste reduction goals;
  • Sustain local industries and jobs; and
  • Create an improved public image for your business.

The Waste Reduction Record-Setters Project fosters development of exceptional waste reduction programs introduced by EPA (Environmental Protection Agency)

These Program include the quantity and type of food discards, availability of space for on-site recovery, existence of haulers and/or end users for off-site recovery, and program costs. Food discard recovery methods include making donations, processing into animal feed, rendering, and composting. Off-site methods involve food discard generators, haulers, and end users.

Food Donations

Non-perishable and unspoiled perishable food can be donated to local food banks, soup kitchens, and shelters. Local and national programs frequently offer free pick-up and provide reusable containers to donors. To encourage food donations, all 50 states and the District of Columbia have enacted “Good Samaritan” laws that protect from liability those donors who take adequate measures to prevent food spoilage or contamination [25].

Animal Feed

Recovering food discards as animal feed is not new. In many areas hog farmers have traditionally relied on food discards to sustain their livestock. Farmers may provide storage containers and free or low-cost pick-up service. Coffee grounds and foods with high salt content are not harmful to livestock. At least one company is using technology to convert food discards into a high-quality, dry, pelletized animal feed. Food discards are also used to make pet food.

Rendering

Liquid fats and solid meat products can be used as raw materials in the rendering industry, which converts them into animal food, cosmetics, soap, and other products.

Composting

Composting can be done both on and off-site. If composting done on-site, necessary to consider carbon/nitrogen ratios. Food scraps provide most of the nitrogen, while bulking agents such as newspaper, cardboard, and wood chips provide carbon.

The moisture and carbon content of food discards will determine how much bulking agent should be added. Temperature and aeration are other important factors that will determine how long it takes materials to compost. Composting can take many forms:

  • Unaerated Static Pile Composting:
  • Aerated Windrow/Pile Composting:
  • In-vessel Composting:
  • Vermicomposting:

6.2 KOREA

The rapidly growing urban population in Korea has generated an ever increasing volume Municipal Solid Waste (MSW or Garbage) which has caused serious environmental and social problem from its ultimate disposal. Food waste which accounts for about 30 percent of urban garbage was collected from the cities of Korea and was treated with EM household recycling. The below table shows that in 1994 the daily production of municipal solid waste was 58,350 metric tons of which 16,140 tons, about 28% was food waste. In 1994, 8796 tons of food waste and daily product was recycle for beneficial use [26].

Disposal of food waste by land reclamation has caused severe problem of malodors and pollution of surface water and ground water. In 1991, the Korean government began other method which allows food waste to be recycled as compost which was used as organic fertilizer and soil conditioner or as animal feed.

6.2.1 Different methods for food waste composting.

Recycled Food Waste (Composting Food waste with Effective Microorganisms)

In 1993 Korean government introduced the project called Recycled Food Waste (Composting Food waste with Effective Microorganisms). They began to compost food waste in the yeonchon and kyongi area of korea using Effective Microorganisms (EM) which is a mixed culture of beneficial microorganisms, as an inoculants. This project was successful in producing high quality compost.

In 1994, they established food waste composting demonstration projects in 12 cities involving some 7,600 households. EM was effective in suppressing malodors during composting and finished compost was shown to be an excellent soil conditioner and organic fertilizer for crop production. [27]

Cooperative Food Waste Composting Project Involving Pusan City and the Pusan Red Cross Society

In 1994, Pusan City and the Pusan Red Cross Society established a cooperative project for composting food waste and utilizing the product as an organic amendment and fertilizer for crops. About 860 households in Pusan City participated in the project which involved collecting and treating food wastes with EM in plastic fermentation chambers. One chamber per household was supplied free-of-charge by Pusan City and the Pusan Red Cross Society. EM effectively controlled malodors during fermentation. Each week the municipal waste authority for Pusan City collected the fermented food waste and transported it to a composting facility for processing into a final product.[26]

Earthworm Production with EM-Fermented Food Waste

Earthworms are produced in Korea as a source of medicinal extracts and as protein. EM-fermented food waste was used as food for earthworms in a demonstration project with considerable success compared with conventional methods.

7. Benefits of Food Waste Composting

7.1 Introduction

Compost is beneficial to soil in many ways. It can improve the properties of soil and growing media physically, chemically and biologically.

Regional and national benefits primarily relate to reduction in water usage, reduced requirement for imported fertilizers, increased productivity and control of soil and nutrient loss to waterways[28].

7.2 Physical Benefits

Physical benefits of compost help in

  • improving soil structure;
  • improving moisture management.

7.2.1 Improved Soil Structure

In fine-textured (clay, clay loam) soils, compost addition reduces bulk density, improves friability and porosity and increases gas and water permeability, thereby reducing the potential for erosion. When used in sufficient quantities, compost resists compaction in fine textured soils, and increases water-holding capacity and improves soil binding in coarse textured (sandy) soils. The soil binding properties of compost is due to its humus content. (Humus is a stable residue from the decomposition of organic matter.) The constituents of humus act as a soil “glue”, holding soil particles together, making them more resistant to erosion and improving the soil's ability to hold moisture.[29]

The increased strength of soils and compaction resistance allows roots to penetrate more easily to find nutrients and water. Heavy soils are also more easily worked, that is, more friable, when the soil organic matter content is high.

7.2.2 Improved Moisture Management

The addition of compost to soil increases the soil water-holding capacity. This is attributed to improved pore size distribution. Pores in the range 0.5-50 microns, called storage pores, hold water necessary for growth of plants and microorganisms. [29]

Increased water-holding capacity provides for greater plant survival, drought resistance and more efficient water utilization. This enables the frequency and intensity of irrigation to be reduced. The addition of compost to sandy soils, in particular, can facilitate moisture dispersion, by allowing water to more readily move laterally from its point of application.

The benefits of improved moisture management also apply on a regional scale, through reduced demand for water for irrigation and drought resistance.

7.3 Chemical Benefits

Chemical benefits of compost use are related to:

  • Soil pH;
  • Increased cation exchange capacity;
  • Nutrient supply.

7.3.1 Soil pH

Soil pH affects the availability and absorption of nutrients by plants, particularly micronutrients. Most compost products have a near neutral or slightly alkaline pH with a high pH buffering capacity, that is, the capacity to buffer or moderate pH changes. Most agronomic crops grow well when the soil pH is between 6 and 7. The buffering capacity of compost stabilises soil pH, that is, it enables it to resist pH change.[30]

Elevation of pH by compost application increase the degree of absorption and, in some cases, precipitation of cadmium, manganese, lead, and zinc in soil particles, resulting in lower bioavailability of these elements to plants.

The calcium in compost provides a small liming effect, increasing the soil pH. It has up to 10 % of the neutralising value of limestone, on a dry weight basis[30].

7.3.2 Increased Cation Exchange Capacity

Cation exchange capacity (CEC) is a measure of the exchangeable cations that the soil can absorb or hold[31]

Examples of cations include calcium, potassium and ammonium. CEC of soils is important in retaining nutrients against leaching by irrigation water or rainfall.

Improving the CEC of soils improves the retention of these nutrients in the root zone.

7.3.3 Nutrient Supply

Compost products contain a large variety of macro nutrients (nitrogen, phosphorous, potassium, calcium, magnesium and sulphur) and micro nutrients (zinc, copper, manganese and boron). However, the nutrient content is lower than commonly used chemical fertilizers[32].

Compost typically provides nitrogen and phosphorous in a slow release form and potassium in a readily available form.

7.4 Biological Benefits

Biological benefits of compost use are related to:

  • Soil micro-organisms;
  • Earthworms;
  • Suppression of soil borne plant pathogens;
  • Weed control.

7.4.1 Soil Micro-organisms

Soil microorganisms include bacteria, protozoa, actinomycetes and fungi. The activity of soil microorganisms is essential in productive soils and for healthy plants. Their activity is based largely on the presence of organic matter.[33]

7.4.2 Earthworms

Earthworm populations can be increased through the addition of compost. The soil mixing and tunneling by the earthworms results in enhanced aeration and water infiltration. Earthworm activities can also nutrient availability for plant uptake.[34]

7.4.3 Suppression of Soil-borne Plant Pathogens

Disease incidence in many plants may be affected by the level and type of organic matter and

Microorganisms present in soils. Increased populations of certain microorganisms may suppress plant such as pythium and fusarium and pests, such as nematodes.[35],[36]

Disease control may be achieved by a combination of factors, such as:

  • Successful competition for nutrients by beneficial micro-organisms;
  • Antibiotic production by beneficial micro-organisms;

Tailored compost can reduce, or replace, the application of pesticides, fungicides and nematocides, which can adversely affect water resources, food safety and worker safety. The use of tailored compost can also be more cost effective than chemical soil treatments, such as methyl bromide[36]

7.5 Disadvantages:

  • Compost bins attract files, maggots and rats
  • Odor Problems
  • Specialized equipment/material requirements
  • Potential for local/state regulation and zoning considerations

8. Conclusion

Excessive food waste and improper food handling have led to overall food scarcity and increase in world hunger. Composting of food waste and the derivative from the compost products offer a wide variety of applications for a range of different markets and can beneficial to soil in many ways. Food waste composting can improve the properties of soil and help in the growth of media structurally (physically), nutritionally (chemically) and biologically.

This research report represents a coming together of many interests from a viewpoint of understanding the food waste and their types from an in-depth perspective. The term composting signifies nature's recycling method which is bio-degradation of organic waste to fertilizers for plant growth. The relatively easy to manage composting from homes to wide range scale for outdoor geographic location for developed or developing countries offer plethora of benefits in a eco-friendly manner which can be incorporated into any waste management plan.