Biowaste-grown live microbial feed additive sustainably and significantly cut enteric methane emissions in Indian livestock

Ruminant enteric methane, the largest agricultural source of CH₄, is a key target in global climate policies. We developed a biowaste-derived live fed microbial (LFM) from fruit- and vegetable residues and evaluated its potential as a scalable intervention to reduce enteric methane while improving animal performance. In controlled in vitro assays and a 98 days in vivo feeding trial in bovine calves (n = 15), LFM at 2% dietary inclusion (dry-matter basis) improved feed efficiency by 30.9%, reduced modelled methane emissions by 25.2%, increased total volatile fatty acids by 45.5%, and lowered NH₃-N by 28.4%. At 3% inclusion, feed efficiency improved by 25.5%, methane emissions decreased by 30.4%, total VFA increased by 43.0%, and NH₃-N declined by 11.7%. Methane abatement was estimated by integrating in vitro and in vivo measurements using an empirically fitted conversion factor and Tier-2-compatible intake models. The IPCC (2006) Tier-2 equivalents indicated ~19% reduction. Scaling to India's livestock herd suggested abatement of 15.4 Mt CH₄ yr⁻¹ (432.3 Mt CO₂-eq yr⁻¹; GWP₁₀₀ = 28) under full adoption, corresponding to ~US$494.1 million annually under the carbon-price assumption used. These findings position biowaste-derived LFM as a circular-economy feed technology capable of simultaneously improving productivity and reducing enteric methane emissions at scale.