Electricity generated from solar and wind has grown rapidly in the past few decades. However, its continued growth is imperiled by the high costs of grid integration. While solar and wind energy enjoy low operating costs, they are intermittent and variable on multiple time scales. Thus they may not be available when needed. Storing electrical energy is costly and so is providing backup power. Thus grid integration costs rise as the penetration of solar and wind electricity increases.
There is a strong positive correlation between installed wind and solar capacity versus the residential energy price in 21 member countries of the European Union. In other words, the price paid by consumers for electricity rises as more electricity from solar and wind is produced. Public support for renewable electricity will most likely be undermined as this trend continues or intensifies with greater penetration of solar and wind into the grid.
Thus to mitigate climate change and provide sustainable electricity to underpin long term prosperity, we must have low carbon electricity that can be supplied on demand to make up for the intermittent and variable nature of wind and solar electricity.
Biogas (roughly 55% methane/45% carbon dioxide) and biomethane (renewable natural gas) are promising biofuels to provide “dispatchable” electricity that can fill in when solar and wind are not available. Biogas can be produced from essentially any organic material via anaerobic digestion (AD), including a variety of wastes, residues and purpose-grown energy crops.
AD is a well-developed, patent-free, mature technology that can be rapidly scaled up. Recent experience in Italy indicates that a doubling time of 18 months for installed AD capacity is possible. Furthermore, the existing natural gas grid provides a low cost means of storing and distributing biomethane where it is needed, in contrast to the expensive and problematic storage and distribution of electricity from solar and wind.
Under policy mechanisms such as California’s Low Carbon Fuel Standard, the production of biomethane from organic wastes is economically attractive today. However, organic waste streams alone are insufficient to achieve the scale necessary for biomethane to meet national needs for low carbon energy. To provide adequate amounts of low carbon biomass, farmers can grow sequential energy crops without reducing food production. Incentives and mechanisms for farmers to produce and then aggregate biomethane are necessary to generate very large scale biomethane to provide diverse low carbon energy services.
Thus biogas and biomethane would seem to merit much greater research, development and public policy support as potential low-carbon fuels that can minimize the costs of integrating increasing amounts of solar and wind electricity into the grid, while also providing other energy services.