Recycling Organic Waste into Fertilizers:
Environmental Benefits

Recycling organic waste into fertilizer is a critical process that converts biodegradable materials into valuable soil nutrients. This waste management method provides significant environmental benefits, including reduced greenhouse gas emissions, improved soil health, and closed resource loops.

With more than 2.3 billion tons of municipal solid waste generated annually worldwide, recycling the organic fraction is becoming critical to achieving sustainable development goals.

Organic waste accounts for a significant proportion of the total waste generated. In the European Union, organic materials account for more than 51% of municipal solid waste in landfills, including food scraps, yard trimmings, wood and paper. Globally, organic waste generation is expected to reach 3.4 billion tonnes in the coming decades, highlighting the urgent need for efficient recycling methods.

Methods of organic waste processing

Composting

Composting is a controlled biological process of decomposition of organic materials with the participation of microorganisms in the presence of oxygen. The process includes the phases of hydrolysis, acidogenesis, acetogenesis and maturation, resulting in the formation of a stable humus-like material. Traditional composting can take from 3 to 6 months, while optimized methods can reduce this period to 2-3 months.

Composting occurs under aerobic conditions, which fundamentally distinguishes it from anaerobic decomposition in landfills. With proper process management, a temperature of 55-65°C is achieved in the thermophilic phase, which ensures the destruction of pathogens and weed seeds. Microbiological activity in compost can increase by 82% compared to untreated soil, which contributes to the formation of a healthy soil ecosystem.

Finished compost contains 40-50% organic matter and has a slow release of nutrients, which provides stable nutrition for plants over a long period of time. The carbon content of compost varies from 10% to 28.5% for garden waste and from 19.1% to 47% for food waste.

Anaerobic fermentation

Anaerobic digestion is a biological process of decomposition of organic materials in the absence of oxygen, resulting in the formation of biogas and digestate. The process occurs in four stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis. In specialized reactors, a temperature of 35-55°C and optimal pH conditions are maintained for maximum process efficiency.

Biogas consists of 50-75% methane and 25-50% carbon dioxide, with small amounts of hydrogen sulfide and water vapor. One kilogram of food waste can produce 300-600 cubic meters of biogas, equivalent to 1800-3600 kWh of energy. Modern anaerobic digestion systems can capture more than 85% of the methane that would otherwise be released into the atmosphere.

The digestate obtained after anaerobic digestion is rich in nutrients and can be used as a liquid fertilizer or subjected to further composting. The organic matter content of the digestate remains high, which helps improve the soil structure and water-holding capacity.

Vermicomposting

Vermicomposting is the process of recycling organic waste using earthworms, usually Eisenia fetida or Lumbricus rubellus. The worms consume the organic material and excrete it as coprolites (worm castings), which are a high-quality organic fertilizer. The vermicomposting process takes 2-3 months and can be done at temperatures ranging from 15°C to 30°C.

Vermicompost contains higher concentrations of nitrogen, phosphorus, potassium, calcium and magnesium compared to traditional compost. It is also rich in beneficial microorganisms, including bacteria, fungi and actinomycetes, which help improve the biological activity of the soil. Studies have shown that the use of vermicompost can increase commercial yields by 26%, total biomass by 13%, shoot biomass by 78% and root biomass by 57%.

The digestive processes of worms are capable of eliminating up to 96% of ingested bacterial taxa, including harmful bacteria such as Escherichia coli and Salmonella spp., making vermicompost a safer option for soil enrichment.

Environmental benefits

Reducing greenhouse gas emissions

Recycling organic waste into fertilizers provides a significant reduction in greenhouse gas emissions. When organic materials decompose in landfills under anaerobic conditions, they produce methane, a greenhouse gas that is 25 to 28 times more potent than carbon dioxide in terms of global warming over a 100-year period.

Food waste is responsible for 58% of methane emissions from municipal landfills and accounts for 24% of all materials entering landfills. Overall, food waste and loss accounts for 8-10% of global greenhouse gas emissions, nearly five times the total emissions from the aviation sector.

Composting organic waste has the smallest carbon footprint, with up to -41 kg CO2e per ton of organic waste. Anaerobic digestion with renewable natural gas production can provide a reduction of -36 kg CO2e per ton of waste if biogas is used to replace diesel. In comparison, landfilling organic waste emits almost 400 kg CO2e per ton of waste.

Recycling all organic matter avoids 40-60% of carbon loss to the atmosphere compared to traditional composting. When implemented correctly, biogas systems can reduce global greenhouse gas emissions by 10% and meet 50% of the Global Methane Commitment targets by 2030.

Soil carbon sequestration

The use of organic fertilizers obtained from recycled waste contributes to the long-term sequestration of carbon in the soil. Compost contains stable organic compounds that decompose slowly in the soil, ensuring the accumulation of organic carbon. During the composting process, about 50% of the carbon from the original materials is lost as CO2, and the remaining 50% is stored mainly in recalcitrant organic compounds.

Research shows that 45% of the carbon added through compost is retained in the soil for 20 years, 35% for 50 years, and 10% for 100 years. When mature garden compost is used as a soil conditioner at a rate of 10 tonnes of dry matter per hectare, carbon sequestration can be equivalent to a reduction of 5,046 kg CO2e over 20 years.

Improving soil organic matter by 1% holds an additional 16,500 gallons of plant-available water per acre of soil at a depth of 1 foot. Soil with 4% organic matter holds more than twice as much water as soil with 1% organic matter.

Improving Soil Health

Organic fertilizers significantly improve the physical, chemical and biological properties of the soil. They increase the cation exchange capacity of the soil, improve structure and aggregation, increase water retention capacity and provide a slow release of nutrients.

Microbiological activity of the soil is a key indicator of its health. The use of biocompost significantly increases bacterial and fungal richness by 7.11% and 5.71%, respectively. Long-term use of organic fertilizers contributes to the enrichment of beneficial microorganisms such as Sphingomonas, Acidibacter, Streptomyces, and the reduction of harmful microorganisms, including Stachybotrys and Aspergillus.

Organic matter can hold up to ten times its mass of water because organic matter particles have a charged surface that attracts water. For every one percent increase in soil organic matter, U.S. cropland could store an amount of water equivalent to the flow of Niagara Falls for 150 days.

Biodiversity and disease suppression

Organic fertilizers promote the development of a diverse microbial community in the soil, which naturally suppresses soil pathogens. Beneficial microorganisms in compost compete with harmful pathogens for resources and space, effectively controlling their development.

Research has shown that vermicompost can suppress diseases caused by pathogens such as Pythium, Rhizoctonia and Verticillium, which are common root disease pathogens in plants. Bio-organic fertilizers stimulate native Pseudomonas populations in the soil to enhance plant disease suppression.

Application of organic fertilizers increases the relative abundance of potentially beneficial bacteria such as Luteolibacter, Glycomyces, Flavobacterium and Flavihumibacter, which are significantly negatively correlated with foliar pathogen incidence.

Nutrient Cycles

Nitrogen cycle

Organic fertilizers play a central role in the nitrogen cycle, providing a slow and controlled release of nitrogen to plants. Unlike mineral fertilizers, which can cause nitrate leaching and eutrophication of water bodies, organic fertilizers mineralize nitrogen gradually according to plant needs.

The ureolytic communities in the soil responsible for the hydrolysis of urea to ammonia are significantly altered by organic fertilizers. Fresh manure has a stronger effect on the composition of the ureolytic community than compost, which is associated with higher nitrogen availability and urease activity.

Organic fertilizers contain nitrogen in various forms: protein nitrogen, amino acids, urea and nitrates. With organic fertilizers, 5-15% of the nitrogen becomes available to plants each year when applied regularly for four or more years, meaning that 20-35% of the nitrogen applied with compost will support plant growth over a three-year crop cycle.

Phosphorus cycle

Phosphorus in organic fertilizers is found predominantly in organically bound forms, which are gradually mineralized by soil microorganisms. The availability of phosphorus from composted and fresh organic materials is usually similar, with responses generally proportional to the total amount of phosphorus applied.

Duck manure enriched biocompost exhibits high phosphorus content, making it an effective phosphorus-enriched biofertilizer. The application of organic fertilizers can increase the availability of phosphates in the soil by 143.26% compared to the control soil and by 7.23% compared to chemical treatment.

Potassium cycle

Potassium in organic waste is usually as available as in mineral fertilizers, meaning it is at risk of being washed out during the composting process. If the potassium can be retained through careful management of the process, the resulting material can add useful amounts of potassium to the soil. Grass and straw compost can contain about twice as much potassium as chicken manure.

Economic aspects

Reducing fertilizer costs

The use of organic fertilizers can significantly reduce the cost of mineral fertilizers. The economic benefit of using organic fertilizers instead of Nitroammophoska varies from 12.61 to 17.43 UAH per kilogram of NPK in the pessimistic scenario, or from 37.83 to 113.30 UAH per ton of organic fertilizer.

According to the optimistic scenario, savings are from 17.00 to 19.45 UAH per kilogram of NPK, or from 51.00 to 126.43 UAH per ton of organic fertilizer. The cost of nutrients in organic fertilizers is 4.5-8.2 times lower than the cost of nutrients in mineral fertilizers.

Production costs

The cost of production of organic fertilizers, depending on the method, varies from 13.69 to 26.85 UAH per ton. When calculating the cost of 1 kg of NPK in samples of organic fertilizers from various farms according to the pessimistic option, it is from 4.13 to 8.95 UAH, and according to the optimistic option - from 2.11 to 4.56 UAH.

Organic farming has been shown to reduce input costs by 30-40% and increase crop yields by 15-25% in various farming systems. In India, farmers who have adopted vermicomposting practices have reported a 30-40% reduction in input costs and a 15-25% increase in crop yields.

Market premium

Organic produce typically commands a significant price premium, which benefits producers. The higher prices for organic produce are due to higher production costs, including certification, labor, and alternative pest and disease control methods. However, this premium is offset by lower costs for synthetic fertilizers and pesticides.

Technological innovations

Modern composting systems

Modern composting technologies include automated temperature, humidity and aeration control systems. Forced aeration and turning systems provide optimal conditions for microbiological processes and reduce composting time.

BTSys technology is an industrial organic waste treatment and recycling system that produces sustainable and effective fertilizer. The closed-loop process completely recycles macronutrients and carbon, converting waste into organomineral fertilizer without environmental damage or pollution.

Biogas plants

Modern biogas plants can process up to 250 kg of organic food waste per day, producing clean gas for cooking or heating. HBG 20 plants include an automatic waste grinding system, which is then automatically transferred to an anaerobic digester for conversion into biogas.

A special anaerobic bacterial mixture, not derived from animal manure, is introduced in tablet form to activate the unit. An industrial computer system controls the unit and uses specialized sensors to monitor temperature, gas pressure and gas level.

Digital technologies

Digital technologies are increasingly being used to monitor and optimize organic waste recycling processes. Remote monitoring systems enable real-time tracking of key process parameters, including temperature, pH, oxygen content, and humidity.

Artificial intelligence and machine learning are used to predict optimal process conditions and automatically adjust parameters. Blockchain technologies are used to track the origin of organic waste and certify the quality of the resulting fertilizers.

Policy and regulation

European Union

The European Union adopted a comprehensive legislative framework for organic waste management as part of the 2018 circular economy package. Key targets include an overall recycling target of 65% of municipal waste by 2035, mandatory separate collection of biowaste by 2023 and a reduction in landfill of municipal solid waste to 10% by 2035.

The revised Waste Framework Directive allows biodegradable and compostable packaging to be collected together with biowaste and recycled in industrial composting and anaerobic digestion. The directive also bans the incineration and landfill of separately collected waste from July 2020.

Delegated Regulation (EU) 2023/1605 defines an end point in the production chain for compost and digestate, after which they are no longer subject to the Animal By-Products Regulation, provided that they are used as component materials in EU fertiliser products.

National Strategies

California passed SB 1383, which requires reductions in methane emissions from dairy farms, livestock, organic waste, and landfills. The law includes steep reduction targets for landfilling organic waste in state landfills: a 50% reduction from 2014 levels by 2020 and a 75% reduction by 2025.

Italy has set a minimum target of 65% for separate waste collection at municipal level. Failure to meet the minimum targets will result in municipalities being charged an additional 20% of the landfill tariff.

France is implementing the AGEC law (Waste Control and Circular Economy Law), which introduces the obligation to separate the collection of bio-waste at source from 1 January 2024. The law provides that every citizen must have “at their disposal a solution allowing them not to throw away their bio-waste” so that it can be recycled.

Sustainable Development Goals

Recycling organic waste is directly linked to several UN Sustainable Development Goals. Goal 12 (responsible consumption and production) includes target 12.5 – by 2030, substantially reduce waste generation through prevention, reduction, recycling and reuse.

Goal 11 (sustainable cities and communities) and Goal 14 (life below water) are also closely linked to organic waste management. Proper organic waste management can contribute to achieving zero waste and zero greenhouse gas emissions from the waste sector.

Regional differences and adaptation

Developing countries

In developing countries in Asia, current urban waste management practices pose a threat to human health and the environment. Biological treatment methods for organic waste, including composting, anaerobic digestion, and mechanical-biological treatment, have a number of well-documented advantages over current and traditional waste management practices.

Smallholder farmers in the Global South can play an important role in methane emission reduction strategies through affordable biodigester technologies. Decentralized composting systems are particularly suitable for rural areas where transportation costs can be prohibitively high.

Industrialized countries

In industrialized countries, the focus is on large-scale, highly automated, centralized treatment systems. Large-scale anaerobic plants in industrialized countries typically produce more electricity than they consume and are often energy independent.

Integrating organic waste management systems with existing water treatment and energy infrastructure can create synergies and improve overall system efficiency.

Challenges and Limitations

Technical limitations

One of the main technical constraints is the need to ensure stable quality and quantity of uncontaminated organic raw materials from households and enterprises. Contamination with plastic, glass and other inorganic materials can significantly reduce the quality of the resulting fertilizers.

Seasonal restrictions on digestate application may require landfilling, which reduces the environmental benefits of anaerobic digestion. In California, solid digestate can only be applied to land for part of the year due to water quality and runoff issues during the rainy season.

Economic barriers

Low landfill costs in some regions without bans on organic waste landfills create economic barriers to the development of alternative recycling methods. Limited, underdeveloped, or poorly understood markets for end products also discourage investment in organic waste recycling.

Competition with alternatives such as fossil fuel-based fertilizers creates additional market challenges. Organic fertilizers are generally less concentrated than synthetic fertilizers, requiring the use of more of them.

Social and regulatory barriers

Obtaining permits for new organic waste treatment facilities or expansion of existing facilities is often difficult due to concerns about odor, noise, and traffic. Educating the public or employees about the importance of separating organic waste requires significant investment in information campaigns.

The lack of harmonized quality and testing standards for compost at the federal level in some countries creates uncertainty for producers and consumers of organic fertilizers.

Future Prospects

Technological innovations

The development of biotechnology opens up new possibilities for increasing the efficiency of organic waste processing. The use of genetically modified microorganisms can accelerate decomposition processes and increase the yield of useful products. Nanotechnology can be used to create more effective catalysts and monitoring systems.

Integrating renewable energy sources with organic waste treatment systems can improve the overall energy efficiency of the process. Solar energy can be used to maintain optimal temperatures in compost heaps, and wind energy can provide aeration.

Circular economy

The transition to a circular economy creates new opportunities to integrate organic waste recycling into broader resource management systems. The principles of the circular economy – reduce, reuse, recover and recycle – are fully consistent with the goals of effective organic waste management.

The development of symbiotic industrial networks, where waste from one enterprise becomes raw material for another, can significantly improve the efficiency of resource use. The integration of agriculture, food processing and waste management systems can create closed nutrient cycles.

Climate adaptation

In the context of climate change, organic waste processing systems must adapt to changing temperature and humidity conditions. Developing climate-resilient processing technologies will help ensure stable operation of systems in different climatic conditions.

Integrating organic waste recycling systems with climate change adaptation measures such as water management and flood protection can provide synergistic effects to increase community resilience.