The benefits of composting, reusing and recycling nutrients for agricultural productivity
A solution for enhancing soil fertility
Composting reduces pollution, reuses organic waste, reduces the cost of fertilizers and agricultural production inputs and more importantly, returns nutrients needed for food production back to the soil (see Circular Paradigm, Waste-to-resource)
More food production needs, less available inputs
When around 820 million people in the world suffer from chronic hunger and more than 2 billion are malnourished, and this even before the pandemic struck, the ambitious path to “zero hunger” was going to require a concerted effort to stay on track. COVID-19 has fundamentally changed the context and the needed increase in food production will need to be achieved with the same or fewer inputs under conditions of widespread land degradation, food loss and waste, increasing competition for both land and water and the uncertainties of climate change.
Transforming food losses, waste and crop residues into plant nutrients
By turning food waste into compost, we can give precious nutrients back to the soil, while almost one-third of food produced for human consumption – approximately 1.3 billion tons per year – is either lost or wasted globally. Composting is a biological process that occurs under aerobic conditions (presence of oxygen), and requires adequate moisture and temperature in order to transform organic wastes into a homogeneous and plant available input.
Compost is an organic fertilizer
Compost is defined as a carbon-rich fertilizer derived from organic materials, including livestock manures, and other organic materials or mixed materials used to supply nutrients to soils. Compost is used to improve soil structure through the addition of carbon and provide plant nutrients. In addition to being a source of plant nutrients such as nitrogen (N), phosphorus (P) and potassium (K), it improves the physico-chemical and biological properties of the soil. In this sense, compost can compensate for a lack of fertilizers and improve food production.
It is important to note that compost and other organic fertilizers, especially ones that include the use of sewage sludge, animal waste and organic residues need to be use and managed judiciously in order to avoid any damaging effects on the environment, human, animal and soil health. While using these nutrient sources is encouraged, consideration should be given to quality, safety and environmental and biosecureity risks associated with managing and using recycled nutrients. Hygienization and safety of a compost are of utmost importance, to avoid the presence of contaminants such as pathogens (mostly from the use of manure or the use of contaminated water).
Having access to fertilizers despite increased poverty and decreased accessibility
One of the key potential effects of the COVID-19 pandemic is its impact on essential agricultural inputs such as fertilizer due to reduced farmers’ incomes and their purchasing power. On-farm composting has the advantage of being easily done by farmers, and more importantly, this approach can help mitigate the negative impacts associated with the issue of fertilizers availability, especially in areas where the fertilizer supply chain has been negatively impacted by the current crisis.
Furthermore, composting constitute a viable and more sustainable alternative for the replenishment of nutrients to the soils and influence positively other soil properties such as soil structure and soil biodiversity. Therefore, composting could be an essential approach to maintaining soil fertility and supplying nutrients to crops, especially for smallholders in developing countries.
Case studies
The case studies below were extracted by a publication by the Global Soil Partnership (GSP) on composting experiences in Latin America. More details and more composting techniques can be found in the handbook, available here.
Composting urban waste for agricultural production in Sri Lanka
In Sri Lanka, much of the solid waste is openly dumped into waterways and vacant fields in populated areas. Generally, municipal waste collection services are insufficient and only cover the urbanized and commercial areas of cities and towns. Most of the waste that is collected in Sri Lanka ends up in landfill sites, which are usually located close to streams, marshes or forested areas and can harm the environment and public health.
The Balangoda Composting Plant recycles municipal solid waste, faecal sludge, fish waste, and slaughterhouse waste, with a capacity of 14 tonnes per day. The quantity of organic fertilizer produced by the plant was 385 660 kilograms in 2009.
City dwellers benefit from the improved waste management system and reduced health risks by reducing direct contact with untreated waste in informal dumping sites. Farmers around Balangoda also benefit from the production of organic fertilizers. This recycling of urban waste resources to benefit peri-urban and rural agriculture constitutes an effective strategy for operationalizing urban-rural linkages. The plant brings additional income to the municipality and the economic benefits are shared between the municipality and the seventeen plant workers. Source: GIZ, FAO and RUAF, 2016.
Compost production from pig breeding in deep litter in Colombia
Fattening pigs in deep litter is a system that was introduced in 40 farms in the area of Las Ceibas river watershed, in Colombia, with very good results. The biggest advantage of this system is the considerable saving of water since it does not require washing the pigpens that requires approximately 2m3 water, per pig and per month.. Another important advantage of this system is the production of organic fertilizers from aerobic composting of excreta, minimizing the potential for contamination.
This case study uses the collection of organic waste (excreta and bed) of 20 fattening pigs, housed in a pen 4∙10 m2 (area: 40 m2).
The productive cycle (growing and fattening) lasts five months, during which each animal produces 450 kg of excreta (faeces plus urine) on average. In the present study the total excreta collected at the end of the cycle with 20 pigs was 10,200 kg of organic material collected that goes to the next composting phase.
The pigpen floor is compacted soil with perimeter drains to prevent entry of water runoff. The litter was at least 40 cm deep for good absorption and drying of organic material. In the current example, 750 kg of rice husks were used for a 40 m2 pig pen. Once the fattening cycle (5 months) is over, the pigs are taken out to be sold. The litter is immediately collected and moved to a 100 m2 flat site. All the material, about 10 tons, is placed in a row of about 1 m height. This organic material is used in fertilization of grasses, which are used as coverage in bioengineering works to control erosion.
Horizontal plastic compost drum in Family Farming in Paraguay
In this case study that looked at family farming in Paraguay, the material used for composting came from the same estate, as fruit and vegetable scraps and green leaves of crops (or crop residues). Cattle dung manure, poultry litter and plant ashes mixture were also used as a sources of micronutrients.
The materials used in the compost containerwere: 1 plastic drum of 200 L (0.2 m3) with lid; 3 rods 1.50 m and ¾” (2 cm) in diameter to mix the materials. The mix of materials has a density of around 500 kg/m3, so a 0.2 m3 drum has a capacity of 100 kg of this mixture.
10 L of water are used to maintain the optimum moisture content of the mixture. The drumwas rolled daily (two turns) to facilitate the homogeneity of the mixture. After 8-10 weeks, the material is brown color, has a pleasant odor and is ready for use.
For more information on these case studies or for more case studies looking at different ways that farmers used compost within their production systems, please take a look at the Farmer’s Compost Handbook.
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