Scientists from the Norwegian University of Science and Technology (NTNU) have assessed the potential for PV and bioenergy deployment on recently abandoned cropland, at a global level.
In the study Optimal combination of bioenergy and solar photovoltaic for renewable energy production on abandoned cropland, published in Renewable Energy, the research team initially identified, through the European Space Agency (ESA) Climate Change Initiative Land Cover (CCI-LC), around 83 million hectares of abandoned cropland between 1992 and 2015. “We identified abandoned cropland by tracking grid cells transitioning from cropland in 1992 to any non-cropland (and non-urban) class in 2015,” the academics specified. “In other words, abandoned cropland includes all grid cells that were registered as cropland in 1992 and not [as cropland] in 2015.” Cropland grid cells that were transformed into urban land were excluded from the survey.
The Norwegian group used the Global Agro-Ecological Zones 3.0 (GAEZ) modeling tool of the Food and Agriculture Organization (FAO) to identify the cropland suitable for bioenergy production and chose three types of perennial grasses, known as switchgrass, miscanthus, and reed canary grass, as the best options for the future deployment of bioenergy due to their high yields, low cost, and environmental co-benefits.
The potential for PV deployment in these areas was assessed through data from the Climate Model (CMCC-CM) atmosphere-ocean general circulation model developed by research institute Centro Euro-Mediterraneo sui Cambiamenti Climatici. These data were then combined to find the optimal distribution of the two energy sources in an analysis that was not only based on energy potential and yield but also included biophysical aspects, local land use, administrative contexts, and socio-economic feasibility constraints.
According to their findings, of the 83 million hectares identified, around 30% is located in Asia, followed by the Americas, with a 28% share, and Africa, with a percentage of 22%. Europe and Oceania had shares of 20% and 5%, respectively. Different reasons may cause the abandonment of these areas, like topography, geophysical constraints, the decline in soil quality, and land degradation among different environmental, socioeconomic, and political factors. “Nevertheless, socioeconomic drivers are of larger importance,” the scientists highlighted.
The potential for bioenergy in the identified areas was estimated at 35 exajoules (EJ) annually, while that of PV was calculated at around 179 EJ. The academics stressed, however, that the extent by which PV performs better than bioenergy differs regionally, with the latter performing better in the tropics compared to higher latitudes. The best locations for bioenergy were found to be in South America, Africa, and South East Asia, while those for PV, although more scattered than those for bioenergy, were identified on the east coast of South America, Central America, parts of Africa, mid-Europe and South East Asia. “The lowest PV yields are found in Scandinavia and North America,” the Norwegian group stated, adding that 75 million of the 83 million hectares originally identified by the survey are really suitable for solar and bioenergy. Of this portion, around 53 million hectares (68%) is considered optimal for solar and around 25 million hectares (32%) for bioenergy, with the former having the largest share in energy generation, at around 91%.
“By only considering the potential primary energy output of each renewable energy option, the PV potential far outcompetes the one of bioenergy crops at a global level,” the researchers concluded. “However, the consideration of different biophysical and socioeconomic factors provides a more realistic comparison [of] deployment potential.” According to them, the combination of these two energy sources in the identified areas can provide a higher level of development compared to considering their deployment as separate cases.
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