The use of microbial agents for the bioconversion of organic waste into fertilizer

How to speed up composting: global experience in using biological agents

mineral fertilizers">The use of mineral fertilizers often leads to a decrease in natural soil fertility. Processing organic waste via composting is becoming an effective alternative. Microbiological agents of fungal and bacterial origin help accelerate the decomposition of plant-based raw materials and improve the properties of the finished fertilizer.

Global practice has accumulated successful experience in the bioconversion of various organic substrates:

• In India, cow manure is mixed with dry leaves. During the decomposition process, the humidity of the mixture is maintained at 50–60% to preserve an aerobic environment.
• In Japan, rapeseed cake and poultry manure are added during the recycling of rice straw, resulting in compost with higher quality indicators.
• In Malaysia, waste from oil palm production (empty fruit bunches and wastewater) is treated with the fungus Trichoderma virens. This reduces the processing time to 21–45 days instead of the standard 4–6 months.
• In Russia, the earthworm Eisenia fetida is used in combination with the strain Trichoderma asperellum MG-97 (VKPM F-765) or the preparation Trichodermin-M to process organic matter. This method cleans the fertilizer of phytopathogenic fungi and gives it growth-stimulating properties.

• Optimal raw material humidity — 50–60%
• Composting period with T. virens — 21–45 days
• Trichodermin-M dosage — 10⁵–10⁶ CFU/kg
• Fertilizer application rate — 2 t/ha

In Kazakhstan, for processing a mixture of poultry manure, mineral fertilizers, rice straw, and rice husks (the latter in the amount of 2% of the total mass), an aqueous suspension of the bacteria Cellucomonas effuse VKPM B-4465 and Bacillus cutaseus VKPM B-4441 is used.

The organic fertilizer obtained via this technology is applied at a rate of 2 t/ha.

In Bangladesh, a bacterial consortium of five strains is used to process potato waste and sugarcane bagasse: Cellulomonas sp., Klebsiella sp., Proteus sp., Enterobacter sp., and Salmonella sp. This combination of microorganisms significantly changes the chemical composition of the substrate:

• reduces carbon content to 26.75%;
• increases nitrogen concentration to 2.34%;
• increases phosphorus content to 1.15%;
• increases potassium content to 1.37%;
• expands the species diversity of bacteria, fungi, and actinomycetes in the finished product.

Selection of Trichoderma strains for the decomposition of cellulose-containing raw materials

Microorganisms used for the processing of plant residues must possess high cellulolytic activity and be competitive. To evaluate these qualities under laboratory conditions, an experiment was conducted to select effective compositions of strains of the genus Trichoderma.

The following biological agents were evaluated in the tests:

• Trichoderma sp. L-3 and Trichoderma sp. L-6 strains (the basis of the microbiological inoculant Resoiler, L);
• Trichoderma asperellum D-11 strain (the basis of the biological product Fungilex, L).

A mixture of leaf litter and grass was used as the experimental substrate. The plant mass was placed in 3-liter glass containers and treated with the culture liquid of the studied fungi in the form of monocultures and mixtures. In the control variant, the residues were treated with tap water.

During the experiment, the substrate was regularly moistened and mixed 1–2 times a week. The dynamics of decomposition were monitored by the loss of mass of the plant residues. For this purpose, 40 and 90 days after the start of the experiment, samples were extracted, dried, and weighed, calculating the weight loss in grams and percentages.

Comparison of monocultures and consortia of Trichoderma strains

During composting of plant waste, the rate of cellulose destruction directly depends on the activity of the decomposer microorganisms. In the experiments, the effectiveness of fungal strains of the genus Trichoderma on leaf litter was evaluated. The Trichoderma asperellum D-11 strain showed the highest activity, ensuring a loss of litter mass of 72.35%. The Trichoderma sp. L-3 and Trichoderma sp. L-6 strains also showed high efficiency, decomposing the substrate by 61.83% and 54.89%, respectively.

The use of pure cultures (single application) on a grass substrate activates the decomposition of organic matter by 86.7–89.5%. However, combining strains into mixtures yields a more pronounced result due to the synergistic effect. Maximum destruction of the grass substrate (92.5%) is provided by a three-component composition combining the strains Trichoderma sp. L-3, Trichoderma sp. L-6, and Trichoderma asperellum D-11.

Selection of the optimal application rate for the biological product

To determine the effective dosage of the three-component consortium, tests were conducted on a mixed cellulose-containing substrate (sawdust, grass, and leaves in a 1:1:1 ratio). This mixture simulates typical organic waste. The treatment was carried out using working solution of the product with an application rate from 0,5 to 2,0 l/t.

1. Prepare a ventilated pile or container and layer the plant residues.
2. Evenly apply the biological product solution to the mass at the specified dosage.
3. Mix the substrate once a week to ensure aeration and maintain a uniform composting process.

By the 40th day, in all variants using microbiological agents, the substrate weight loss exceeded the control values. The most intense organic decomposition was recorded at application rates from 1,0 to 2,0 l/t — the weight loss was 43,5–50,2 %. By the 90th day, this trend persisted, and substrate decomposition in the effective variants reached 66,9–71,3 %.

• Maximum grass decomposition by the consortium — 92,5 %
• Ratio of sawdust, grass, and leaves in the substrate — 1:1:1
• Recommended application rate of the biological product — 1,0 l/t
• Weight loss of the mixed substrate on the 90th day — up to 71,3 %

3. Dayanand, Sh. Bioconversion of flowers waste: Composting using dry leaves as bulking agent / Sh. Dayanand, D. Yadav Kunwar // Department of Civil Engineering, S.V. National Institute of Technology, Surat, Gujarat, India. – 2017. – Vol. 22, № 3. – Р. 237–244.

Method for obtaining compost: pat. 21700, Kazakhstan, IPC: C05F 11/08 / Kh. Dzhamantikov, E. Kh. Dzhamantikov, I. E. Smirnova, A. B. Abzhalelov, M. Kh. Dzhamantikova. – Published 25.06.2009.

6. Sarker, T. C. Physico-chemical profile and microbial diversity during bioconversion of sugarcane press mud using bacterial suspension / T. C. Sarker [et al.] // Not. Sci. Biol. – 2013. – Vol. 5, № 3. – P. 346–353.

7. Bioconversion of empty fruit bunches (EFB) and palm oil mill effluent (POME) into compost using Trichoderma virens / R. Dayana Amira [et al.] // African J. of Biotechnology. –

2011. – Vol. 10, № 81. – P. 18775–18780.

Method for processing organic waste: pat. 2 467 989 C2, IPC: C05F 11/08 / A. V. Kurakov, V. S. Sadykova. – Published 27.11.2012.

M. V. Fedarovich 1, D. V. Voitka 1, I. I. Poloz 2 RUE «Institute of Plant Protection», Priluki, Minsk region SSI «Institute of housing and communal services of the National Academy of Sciences of Belarus», Minsk

DEVELOPMENT OF A COMPOSITION OF

MICROBIAL AGENTS FOR THE BIOCONVERSION

OF MUNICIPAL SOLID WASTE AND CELLULOSE-

CONTAINING MATERIALS IN THE PRODUCTION OF

Summary. The selection of a combination of Trichoderma genus fungi strains in terms of cellulolytic activity using organic substrates was carried out. The mixture of Trichoderma sp. L-3 + Trichoderma sp. L-6 + Trichoderma asperellum D-11 strains had the greatest cellulolytic activity – the decomposition of the substrate reached 92,5 %. The most effective dosage of this fungal mixture was a consumption rate of 1.0–2.0 l / t – on the 40th day, weight loss was 43,5–50,2 % of the substrate weight, on the 90s – 66,9–71,3 %.

Key words: bioconversion, composting, cellulose-containing substrates, Trichoderma, strains, cellulolytic activity.