Vikram Khajuria

Biogas Digestate Products India has one of the world’s highest installed bases of domestic biogas plants (about 5 million) and commercial biogas plants (hundreds) at dairies, food processors, distilleries and municipal waste sites. The Satat Scheme has also introduced a compressed biogas plant (CBG) and MNRE is supporting fresh biogas capacity. However, in this extensive installed base, the digestate (liquid and solid residue after the energy has been extracted from the waste material as biogas) is not adequately managed and monetized. Most biogas plants just release liquid digestate into the adjacent agricultural land or water bodies and solid digestate piles up in pits, without making any effort to utilise them commercially. The digestate is not waste, but the best liquid organic fertilizer for Indian farmers. While composting and raw manure must undergo weeks of soil mineralisation before the available N can be absorbed by plants, anaerobic digestion breaks down complex organic nitrogen (protein and amino acids) quickly into ammoniacal nitrogen (NH₄-N) and is readily available for plant uptake without requiring weeks to mineralise the soil. Liquid digestates produced by well-managed biogas plants is a complete NPK fertiliser, consisting of 1.5–4% N, 0.8–2% P₂O₅ and 2–4% K₂O on dry matter basis. It has been consistently proven that application of digestate increased crop yields by 15–30% compared to the same mineral fertiliser application, which is probably due to growth hormones and beneficial microorganisms present in digestate. Explore This Book: Handbook on Biogas and Its Applications Top 6 Products from Biogas Digestate 1. Liquid Bio-Fertiliser (Direct Application Grade) This is because the digestate of food, agricultural and dairy waste biogas plants can be filtered at the plant (to remove fibre >1 mm) and quality tested before being sprayed directly onto crops in both drip irrigation or sprinkler irrigation systems. Bulk liquid bio-fertiliser (Rs. per unit) 200–300 litre tankers at Rs. 2,000–5,000 per tonne (Rs. The biogas plant is serving the organic and conventional farmers within 50 km radius. 2. Concentrated Liquid Bio-Fertiliser (Evaporation) The multi-effect evaporators enable digestate to be concentrated to 3-4 times its original concentration (from 1.5 % dry solids to 5-6 % dry solids) and allows for a more economic transport over longer distances for the bio-fertiliser. The digestate is produced in concentrated form (20–25% DS) in Rs. The cost of 20 litre containers is Rs. In urban horticulture and hydroponic crop production, premium prices are obtained for 150 – 300 per litre. A digestate concentration evaporation system: 50–150 lakh. Get Detailed Project Report (DPR): Biotechnology, Enzymes & Organic Farming Guide 3. Separated Fibre Compost (Press Cake) Organic compost material (25–30% DS) is produced by screw press separation of digestate to solid press cake and into liquid fraction, which can be stacked and transported. Granular Organic Compost for bagged retail is prepared by pressing the fibre cake and after drying and bulking agents, the compost is obtained at the retail price of Rs. 5,000–10,000 per tonne. Screw press separator and compost yard: Rs. 30–80 lakh. 4. Nutrient-Rich Irrigation Water (Fertigation) Using filtered digestate in on-farm irrigation systems (such as drip and furrow irrigation) to contracted farmers provides a complete service which can replace 30-50% of mineral fertiliser need. The operators of biogas plants establish long-term agreements with farmer clusters within 5 km of the plant, providing digestate via stationary pipelines or mobile digestate tank systems. 5. Dried Organic Fertiliser Granules Press cake from digesters is further dried (rotary dryer) to less than 10% moisture, and subsequently granulated to yield organic fertiliser granules which are easily spread mechanically and sold in the retail market. For the same, the FCO certified dried digestate granules sell for Rs. Premium organic fertiliser markets: 6-12 tonnes per tonne. Investment in the dryer and granulation line is Rs.: 40–120 lakh. 6. Algae Cultivation Substrate Microalgae (Spirulina/Chlorella) cultivation in raceway ponds or photobioreactor systems can be done with high nutrient liquid digestates diluted with water which serve as a perfect growth medium. Nitrogen and phosphorus (nutrient polishing) removed by algae at digestate water is converted to algal biomass with economic value of Rs. Nutraceutical, animal feed, and biofuel applications: 200-800 per kg. A digestate fed algae pond system: 30–100 lakh. Investment and Market Summary Product Investment (Rs.) Price Key Buyer Liquid Bio-Fertiliser 10–30 lakh Rs. 2,000–5,000/MT Organic/Conv. Farmers Concentrated Bio-Fertiliser 50–150 lakh Rs. 150–300/litre Urban Horticulture Fibre Press Cake Compost 30–80 lakh Rs. 5,000–10,000/MT Organic Farmers, Export Organic Fertiliser Granules 40–120 lakh Rs. 6,000–12,000/MT Premium Organic Market Algae Biomass (on Digestate) 30–100 lakh Rs. 200–800/kg algae Nutraceuticals, Feed Farmer Contracts: Building the Digestate Market Utilisation of digestate is only feasible if reliable farmer buyer relationships are established within the economic transport distance from the biogas plant. A 50 km radius around a large biogas plant contains tens of thousands of farmer fields, which however, need systematic market development, demonstration plots in which digestate crop response is demonstrated and infrastructure for delivery. The most successful digestate utilisation model in India is the biogas plant operators forming partnerships with Farmer Producer Organisation (FPO) where FPO provides farmer market aggregation, the operator supplies digestate at a cost below mineral fertiliser equivalent, and both parties benefit from the partnership. This FPO – biogas partnership model is being actively promoted by NABARD and the State cooperative departments. Related Article: Compressed Biogas Export India Opportunities That Can Earn ₹8 Cr/Year Digital Platforms for Digestate Marketing The agri-tech ecosystem in India is maturing to create online platforms that allow organic fertiliser producers (biogas plant digestate suppliers included) to connect with farmer buyers directly instead of through the traditional distributing chain to enhance farmer and producer margins. DeHaat, Ninjacart, AgriBazaar etc. are developing organic input procurement wings that will link the organic input producers to their farmer network. Aqgromalin (an aquaculture focused agri-platform) collects fish and shrimp farm inputs such as organic fertilisers. They offer the following services for biogas plant digestate producers: nationwide farmer buyer access beyond the geographical reach, digital payment and invoicing system, and quality test by the platform. Agri-tech platforms