WET/GREEN WASTE TO COMPRESSED BIOGAS: NAPIER GRASS AS A DEDICATED FEEDSTOCK FOR A DECENTRALISED WASTE-TO-WEALTH MODEL IN SEMI-ARID MAHARASHTRA

This study establishes Napier grass as a highly productive feedstock for decentralised compressed biogas in the semi-arid irrigated regions of Maharashtra. Under a 60-day, six-harvest cycle, one acre yields 109.15 t fresh biomass, 31.00 t dry matter and 26.23 t volatile solids per year. The 60-day maturity stage offers the most balanced biochemical condition — 71.6% moisture, 84.6% volatile solids and a C/N ratio of 23.4 — and, when treated with 2% NaOH, achieves the highest methane yield of 317 mL CH₄/g VS, a 35.5% improvement over untreated biomass that demonstrates the effectiveness of mild alkaline pretreatment in disrupting lignocellulosic resistance. At field scale, the model delivers 8,315 m³ CH₄ per acre annually, upgradeable to 9,077 m³ of IS 16087:2018-grade CBG at 91.6% methane purity and equivalent to 297,677 MJ (about 82,688 kWh). It avoids roughly 26.5 t CO₂e, produces 16.57 t of FCO-compliant digestate, and yields a gross profit near ₹3.10 lakh per acre per year, providing a strong foundation for the system's energy, environmental and economic merits. Future work should advance to Phase-II pilot-scale validation under real field conditions, examine year-round co-digestion with municipal wet waste, quantify purification, compression, storage and transport costs, and use GIS-based site selection to guide the placement of decentralised CBG plants across Maharashtra — thereby converting waste into wealth in a genuinely circular, low-carbon energy system.

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