Is small-scale upgrading of landfill gas to biomethane for use as a cellulosic transport biofuel economically viable?

Landfill gas (with methane content of 35-55%) adds significantly to global warming if released to the atmosphere. Under the EU Landfill Directive, all landfill sites are obliged to collect this gas if supplied with biodegradable municipal waste. Landfill gas (LFG) can be (i) flared, (ii) combusted to produce electricity, or (iii) upgraded to biomethane. The last scenario is of special interest. In the USA, LFG is now classified as a cellulosic biofuel; in the EU, there is a mandatory target of 10% share of renewables in transport by 2020. A significant challenge for upgrading LFG to biomethane is the high nitrogen content resulting from negative pressure in the landfill. Cost analyses were conducted to compare three technology solutions for LFG upgrading with accessible LFG flow of 250-500 m³/h. If injection to the transmission grid is considered, then a single-step pressure swing adsorption (PSA) system may be viable. The optimal solution suggested is an on-site service station; the cost of this system (including propane addition and service station) was assessed as e0.84/m_n ³ LFG biomethane. This required a subsidy of e0.55/m_n ³; this is available in Ireland under the Biofuel Obligation Certificate scheme.