Biomass production in South Africa largely follows a climatic gradient primarily driven by rainfall, with the highest biomass production occurring within the country’s eastern regions or near the coastline.

Within the content of the BioEnergy Atlas, productivity is described as the rate at which biomass is produced. There are two basic types of productivity: gross and net.

• Gross primary productivity, or GPP, is a measure of the total amount of carbon captured by plants as a result of photosynthesis (Amthor and Baldocchi, 2001)
• Net primary productivity, or NPP, is the difference between gross primary productivity and the amount of carbon released into the atmosphere due to cellular respiration. NPP can be used as a rate at which energy is stored as biomass by plants or other primary producers and made available to the consumers in the ecosystem (Schultze, 2007).

Net Primary Productivity is viewed as a raw potential or baseline for biomass production (Schultze, 2007), and this is extensively modified by land use. Hence, the local soil types, current land cover, extent of degradation, and improved yields due to intensive agriculture all play a role in modifying the baseline NPP.

Figure 1: Average annual Net primary Production for South Africa (DFFE, 2015)

MetaData

Biomass production in South Africa follows a climatic gradient, with the primary climatic variables affecting Biomass production being precipitation (Hugo W. (Ed). 2015. South African  BioEnergy Atlas.)

South Africa generally experiences temperate conditions throughout the year due to its subtropical location, but the moderating effect of the Atlantic and Indian Oceans and its varied topography result in a great variety of climatic zones, ranging from the dry north-western to the wet eastern regions of the country. Most of South Africa is semi-arid and water-stressed, with an average rainfall of about 450 mm, approximately 60% of the world average (Schulze, 2007).

Precipitation in South Africa is highly variable, with an uneven spatial distribution and seasonality of rainfall. The eastern and southern parts of the country receive significantly more rain than the northern and western regions. While most of the country is generally a summer-rainfall region, the extreme southwest has a Mediterranean climate characterised by marked aridity during summer months. The rainfall in this region occurs predominantly during the winter period (Tyson and Preston-Whyte 2000).

Figure 2: Mean annual precipitation (mm) (Schultze and Lynch, 2007)

MetaData

Land use and Landcover changes dramatically modify the basal net primary productivity. Practices such as intensive agriculture can significantly increase the volume of biomass produced in an unproductive area, whereas changes from one land cover type to another, such as forestry to crop agriculture would have the opposite effect. Processes such as urbanisation reduce the areas for biomass production, but at the same time, activities such as the transportation and production of fuel and food for growing urban populations, as well as the resultant waste streams, may make significant point or distributed contributions to the availability of biomass.

Figure 3: Landcover of South Africa (Broad Parent Classes) (DFFE, 2014)

MetaData

The potential available land for biomass production has competing interests for land use. In South Africa, these competing interests include:

A. Current agricultural land and food security: Ensuring food security is considered a priority, thus projections of the amount of available land that could potentially be used for bioenergy production need to quantifications and projections of:

1. Future population: A growing population will require additional food production, and if the relative affluence also improves, consumption patterns are likely to change.
2. Improved yields: It may be possible, all other things being constant, to repurpose some farmland for bioenergy use if yields of traditional crops increase significantly.
3. Climate change: The far future may require additional farmland for some crops due to changing conditions, while the productivity of others could increase due to higher temperatures and CO2 concentrations. The net effect of this is a change in the quantum of farmland is required to maintain the status quo.

B. Commercial forestry: Waste products from the Forestry Industry have the potential to be used as a bioenergy feedstock; however, there are management considerations regarding the potential nutrient loss as a result of removing in situ forestry residue that need to be understood. In the BioEnergy Atlas for South Africa, we assume that the existing plantation areas will not be repurposed but that a portion of forestry residue is available for beneficiation.

1. The BioEnergy Atlas has collaborated with the Institute for commercial forestry research (ICFR) to develop a toolkit for assessing the potential nutrient losses associated with varying levels of forestry residue removal and site soil characteristics.

C. Urban and mining areas: These are by definition not available for biomass production, but rehabilitated mining land could support biomass feedstock streams. Future urban growth would contribute to the availability of domestic or industrial waste.

1. These are currently proclaimed as national or provincial parks, and it is doubtful that biomass will be obtained from these areas, except for invasive species.
2. National protected areas expansion strategy: These areas have been identified, but not proclaimed, as possible future protected areas. Depending on the trade-off between conservation and energy diversification, a variable portion of these areas could be considered for biomass generation. Invasive species from these areas are considered part of the available biomass.
3. Ecosystem services: Some areas of the country, while not protected, are critical to preserving ecosystem services, and water is the most important consideration here. Again, a trade-off between conservation and energy diversification determines to what extent these areas are considered for biomass cultivation, and invasive species in these areas are included in estimates.
4. Sensitive biodiversity areas: These are subject to the same trade-offs and considerations discussed above.

Non-usable land These are areas that may or may not be suitable for biomass generation but are excluded based on accessibility, slope, soil conditions, or other factors that will make sustainable biomass generation difficult.

The BioEnergy Atlas presents a number of different feedstocks that can be sourced from different landcover types – these include: