Methane from Rwanda's solid waste disposal sites, 1960 to 2030.

The question

How much methane do Rwanda's solid waste disposal sites release, and how will that change to 2030? Methane from decomposing organic waste is a major part of the waste sector's contribution to a national greenhouse gas inventory, and it builds up over decades rather than years.

Method

The study applies the IPCC First Order Decay (FOD) model, which assumes that the degradable organic carbon in deposited waste breaks down gradually, producing methane and carbon dioxide, with emissions highest in the first decades after deposition and declining as the carbon is consumed. Because the model needs at least fifty years of data to be tolerably accurate, waste deposition was reconstructed from 1960 and projected to 2030.

Of the three IPCC tiers, the study uses Tier 2: country-specific, high-quality activity data on past and present waste disposal, combined with IPCC default parameters.

Results

• Municipal solid waste deposited in disposal sites rose from an estimated 580 Gg in 1960 to 1,041 Gg in 1980, 1,581 Gg in 2000 and 2,601 Gg in 2020, and is projected to reach 3,182 Gg in 2030.
• Industrial waste deposited rose from 168 Gg in 1960 to 302 Gg in 1980, 458 Gg in 2000 and 754 Gg in 2022, with 922 Gg projected for 2030.
• Annual methane emissions from disposal sites grew from 28 Gg CO2-eq in 1965 to 49 Gg in 1980, 68 Gg in 2000 and 122 Gg in 2020, and are projected to reach 157 Gg CO2-eq in 2030.
• Within harvested wood products, garden waste dominates: 13 Gg CO2-eq of methane in 1965, 45 Gg in 1999, 73 Gg in 2020 and a projected 94 Gg in 2030, against 3 Gg from wood products and negligible amounts from paper.

Team

The modelling was carried out by Ekaba Bisong and Taiwo Adediran.