5.3.2 Fossil fuel and nuclear footprints
The land footprint of fossil fuels is mainly associated with their extraction. Coal mining is the most land-intensive, particularly from open-cast pits. Coal mines also tend to have large impacts on existing water resources and surrounding land-use systems. In some countries, land reclamation is a common practice after a mine has been exhausted or otherwise decommissioned, although reclaimed mining land tends to have significantly lower levels of biodiversity and ecosystem services than land that has not been mined.
Oil and gas extraction, both onshore and offshore, usually involves smaller direct land-use footprints per unit of energy supply than coal. However, there can be additional land and environmental impacts from contamination – from leaking oil storage or pipelines, for instance. Oil and gas extraction is increasingly making use of enhanced recovery technologies such as hydraulic fracturing (fracking); these processes increase the land footprint of extraction and generally have greater impacts on biodiversity, water systems and habitats.
3m hectares of land in North America was devoted to oil and gas development from 2000 to 2012.
Although the land footprint per unit of energy for fossil fuels is small, the aggregate scale in absolute terms can be significant. In North America, approximately 3 million hectares (ha) of land (an area about the size of Belgium) was devoted to oil and gas development from 2000 to 2012. In California alone, there are an estimated 105,000 active oil and gas wells (as of 2018); coupled with the associated roads, storage facilities, fuelling stations, oil refineries and pipelines, this infrastructure is estimated to occupy at least 670,000 ha, about 1.6 per cent of the state’s land area.
The direct land use from nuclear power is very small (see Table 2). However, the overall footprint expands considerably when the area of land required for mining uranium ores, waste storage and disposal is factored in. Nuclear accidents, of course, have the potential to affect much wider areas. The two exclusion zones created after the Chernobyl disaster in 1986 cover almost 480,000 ha, while the Fukushima exclusion zone in Japan is 31,000 ha in size.
5.3.3 Renewables’ direct land footprints
Solar and onshore wind power have high land-use intensities when compared with thermal power stations. This argument is sometimes used against the use of renewables. For example, according to the US Nuclear Energy Institute, solar power production uses up to 75 times more land than nuclear power does, while wind power uses up to 360 times more land. A criticism of a 2018 proposal in the California state legislature to transition the state to 100 per cent renewable energy by 2045 claimed that it would ‘require wrecking vast onshore and offshore territories with forests of wind turbines and sprawling solar projects’.
However, such comparisons are misleading. They ignore the co-availability for other uses of the land on which renewables facilities are sited; these uses include agriculture (crops and animal pasture), forests and other ecosystem services. Within onshore wind farm boundaries, for example, approximately 90 per cent of the land is not occupied by wind power equipment. According to a US National Renewable Energy Laboratory (NREL) study, even though the total area per unit of energy for onshore wind ranges between 12 and 57 ha per megawatt (ha/MW) of output capacity (a typical new utility-scale wind turbine is about 2 MW), less than 0.5 ha/MW is disturbed permanently and less than 1.5 ha/MW is disturbed temporarily during construction.
Utility-scale solar PV systems can also coexist with other forms of land use, particularly agriculture. Such ‘agrivoltaic’ systems have been widely installed in many locations over the last decade, with crops sited between solar arrays, underneath them (the shade provided by these arrays can improve productivity for some crops) or in combination with greenhouses. Solar thermal collectors for water or space heating are typically roof-mounted on individual buildings, as are small solar PV systems (250–400 W per panel), and such installations thus avoid any direct land use. In Germany, where there are over 2.2 million grid-connected PV systems (with an aggregate capacity of some 60 GW), rooftop installations make up 70 per cent of the total installed PV capacity.
Another NREL assessment concluded that in terms of direct land-use requirements in the US, the capacity-weighted average for installed solar PV capacity is 3 ha/MW. In terms of actual electricity production, solar PV has an average total land-use requirement of 1.5 ha/GWh per year, and an average direct area requirement of 1.3 ha/GWh per year. Based on this analysis, meeting current global electricity demand purely from utility-scale solar – however unlikely an ambition – would require the use of just 32 million ha, little more than the area of Poland. Adair Turner, the first chair of the UK’s Committee on Climate Change, has anticipated the potential land-use demand succinctly: even allowing for projected future population growth and increased demand for energy, ‘estimated space requirements for solar energy sufficient to power the entire world are reassuringly trivial, at 0.5–1 per cent of global land area’.
Of course, there are also indirect land-use impacts from the extraction of the materials used in the construction of renewable energy facilities, but for solar and wind these impacts are small. One US-focused study estimated the land use associated with mining for materials at 0.11 ha/MW for wind and 0.06 ha/MW for solar PV, compared with fuel production areas of 0.29, 0.52 and 0.58 ha/MW for coal, gas and nuclear power plants respectively.
Large-scale hydropower, which involves storing water in reservoirs behind dams, necessarily inundates land. This means that hydropower often has large localized land footprints as well as other impacts on upstream and downstream ecosystems. The direct land-use intensity of an individual hydropower system varies, depending on its size and the local topography: hydropower plants in flat areas tend to require much more land than those in hilly areas or canyons, where deeper reservoirs can hold greater volumes of water in smaller spaces. In contrast, the land footprints and biodiversity impacts of run-of-river hydropower plants, and of mini (<10-MW) or micro (<1-MW) hydropower systems integrated into water flows, are much smaller, as these do not require large reservoirs.
Dams have significant negative biodiversity impacts through destruction of habitats and obstruction of fish migration patterns.
A review of the area of land flooded by selected individual hydroelectric systems in countries on all continents found that the land intensity varied between 0.23 and 15.64 ha/GWh. The largest such system in terms of power generated – the Itaipu dam on the border between Brazil and Paraguay – was found to have one of the smallest footprints per unit of energy, at 1.26 ha/GWh (on a total inundated area of 115,700 ha). However, additional calculations for other dams in South America not covered by the specific estimates above suggested far higher land-use intensities, of around 10–30 ha/GWh for large plants and 75–175 ha/GWh for smaller plants. Dams also have significant negative biodiversity impacts through destruction of habitats and obstruction of fish migration patterns.
5.3.4 The emergence of large battery storage sites
Greater dependence on renewables will require greater flexibility of power systems to account for increased daily variability in generation. One of many technologies with the potential to increase such flexibility is battery storage. The cost of battery production is falling sharply, and can be expected to continue doing so.
While large-scale battery storage is in its infancy, indications of its land footprint are beginning to emerge. Extrapolating from the efficiencies of the world’s largest battery storage facility, in Florida, we estimate that providing enough battery storage for a single day’s power supply globally would require about 1.3 million ha of land, a little less than the area of Montenegro. Storage options other than batteries also exist – and more are likely to emerge. Currently the most used is pumped-hydro storage.
5.4 Land requirement for renewables in 2050
Drawing on the REmap energy scenario and the land footprints of the major non-biomass renewable energy technologies listed in Table 2, we calculate the global land requirement of solar PV, CSP, onshore wind and hydropower in 2050 to be around 20 million ha; this estimated area increases to 41.9 million ha with the inclusion of battery storage. This land footprint, including storage, is equivalent to 0.86 per cent of global agricultural land, or 1.01 per cent of the area defined as ‘other’ by the Food and Agriculture Organization of the United Nations (FAO). Less than 3 per cent of this ‘other’ land is urban in all regions considered except Europe, where around 12 per cent of such land is urban.
As already noted, it has been estimated that 0.5–1 per cent of the global land area would be required for solar to power the entire world. By way of comparison, under REmap we find that 0.32 per cent of the global land area would be required by renewables excluding biomass, keeping in mind that the REmap scenario envisages non-bioenergy renewables providing only around 23.4 per cent of total energy supply.
