There is an increasing interest worldwide on developing sustainable bioenergy alternatives for low competitive lands where food production profitability is scarce or where soils and climates are not suited for traditional activities or have no market access and low competitiveness. Some examples of this are present in several regions in the world where climate and soil conditions limit the number of alternatives for farmers determining too high costs to compete with other regions, or where market access is not as large as needed to allow large scale production for specific products that can be grown there.
But what to expect about biofuels and bioenergy on marginal lands?
We know that marginal lands, produce marginal yields and it is reasonable to expect to low “marginal” profits as well. Several limitations to the expansion of energy crops have been analyzed in recent years encouraging researchers, governments and companies to change their views on bioenergy sustainability. In the last decade, most relevant arguments from detractors of bioenergy crops global expansions faced discussions on land availability constraining food security. This is particularly relevant when several crops before assumed to potentially occupy marginal lands and produce first generation biofuels, have shown many constraints regarding sustainability indicators . Therefore, policies on the promotion of bioenergy crops shifted from grain (cereals and oilcrops) to lignocellulosic raw materials looking for more sustainable processing pathways and bioenergy chains.
It seems reasonable to think that producing bioenergy on lands with low and very low productivity could derive into high inputs easily. A farmer trying to produce any crop species in marginal sites, would eventually require nitrogen, irrigation or many other inputs that could imply fossil sources in the life cycle assessment, thus having an important implication and impact on the sustainability criteria (low emissions, low fossil energy inputs per energy output unit, low impacts to water, air and soil, etc.). Before going ahead, let’s consider what we do and the current agricultural systems today and sustainability.
New policies are also needed to accelerate the transition to bioenergy produced from feedstocks such as cellulosic crops grown in sustainable systems. These policies include research and development on feedstocks such as native perennials, incentives for bioenergy production facilities with a preference for local ownership, and programs that help farmers make the transition to growing feedstocks in sustainable agronomic systems.
The fact is that perennial grasses aerial net productivity is between 3 and 10 tons per hectare per year and fossil energy inputs required are really low. Having the right processing technology to produce energy could derive into a very sustainable renewable production system to add to existing activities in the rural sector. Its promotion help to conservate green covers, avoid erosion and mitigate climate change negative effects.
Several studies have been analyzing the interaction and sustainability of bioenergy crops perennial systems. As we have pointed in many other posts in our blog (see 7 alternative bioenergy crops for marginal lands) there are many options to consider. Today, grasslands are occupied mainly for livestock production and the first question to make is: how bioenergy crops could be integrated when land availability could be limited and food production competition may occur where livestock (dairy, meat, cheese, milk and many products) are produced? Here a nice video on all this:
Two important studies have confirmed that grasslands could be one the most sustainable bioenergy systems when managed properly. We attached both abstracts from the publication contents here:
Carbon debt of Conservation Reserve Program (CRP) grasslands converted to bioenergy production
Over 13 million ha of former cropland are enrolled in the US Conservation Reserve Program (CRP), providing well-recognized biodiversity, water quality, and carbon (C) sequestration benefits that could be lost on conversion back to agricultural production. Here we provide measurements of the greenhouse gas consequences of converting CRP land to continuous corn, corn–soybean, or perennial grass for biofuel production. No-till soybeans preceded the annual crops and created an initial carbon debt of 10.6 Mg CO2equivalents (CO2e)·ha−1 that included agronomic inputs, changes in C stocks, altered N2O and CH4 fluxes, and foregone C sequestration less a fossil fuel offset credit. Total debt, which includes future debt created by additional changes in soil C stocks and the loss of substantial future soil C sequestration, can be constrained to 68 Mg CO2e·ha−1 if subsequent crops are under permanent no-till management. If tilled, however, total debt triples to 222 Mg CO2e·ha−1 on account of further soil C loss. Projected C debt repayment periods under no-till management range from 29 to 40 y for corn–soybean and continuous corn, respectively. Under conventional tillage repayment periods are three times longer, from 89 to 123 y, respectively. Alternatively, the direct use of existing CRP grasslands for cellulosic feedstock production would avoid C debt entirely and provide modest climate change mitigation immediately. Incentives for permanent no till and especially permission to harvest CRP biomass for cellulosic biofuel would help to blunt the climate impact of future CRP conversion.
Nitrogen and harvest management of Conservation Reserve Program (CRP) grassland for sustainable biomass feedstock production
The Biomass Regional Feedstock Partnership has identified grasslands planted under the Conservation Reserve Program (CRP) as a potential source for herbaceous bioenergy feedstock. The goal of this project is to assess the yield potential of CRP grasslands across diverse regions. Consistent with that goal, the objective of this project was to establish yield potential and quality parameters for several different CRP grasslands, representative of different growing environments. Standard field scale agricultural practices were used as management guidelines at each location. The test locations were identified and established based on known regions containing concentrated tracts of CRP grassland and represented variable climatic parameters and production histories. Biomass production potential for CRP land dominated by either warm- or cool-season grass mixtures in each location was evaluated over the course of three growing seasons (2008, 2009, and 2010). Specifically, a mixture of warm-season perennial grasses was evaluated in North Dakota, Kansas, and Oklahoma, while a cool-season mixture was evaluated in Montana, Georgia, and Missouri. Maximum biomass yields for the three warm-season CRP sites ranged from 4.0 to 7.2 Mg ha−1 and for the three cool-season CRP sites 3.4–6.0 Mg ha−1. Our results demonstrate that CRP grassland has potential as a bioenergy feedstock resource if the appropriate management practices are followed.
Interesting links and articles: