Bioenergy crops in marginal lands have been always  a focus of attention for researchers, bioenergy companies and governments. But those areas would clearly have lower yields. Are lower cost feasible in those regions?. Do lower cost per hectare determine lower  inputs and delivered biomass costs per ton in the gate of our facilities?

The problem:  Energy “miracle” crops with high inputs (nursery, irrigation) expecting  high yields even in marginal areas

Several companies in the world are looking to expand energy crops in marginal areas. Energy  crops like Arundo donax, Miscanthus, short rotation coppice (SRC) with Eucalyptus, poplar, willow as well as bamboo and many other possible feedstock are being analyzed and demonstrated in many projects. Evidence of this can be explored in many publications and reports where several alternative energy crops require high inputs that determine a high yield expectation to perform well when environmental aspects and production costs are considered.  Check for example some sound publications:

• Costs of producing miscanthus and switchgrass for bioenergy in Illinois (44-80 U$D / odt)
• The economical and environmental performance of miscanthus and switchgrass production and supply chains in a European setting (84-136 U$D/odt)
• Examining the economic feasibility of miscanthus in Ontario: An application to the greenhouse industry (78 to 105 U$D/odt)
• Costs of supply chains of Miscanthus giganteus
• Economics of switchgrass and miscanthus relative to coal as feedstock for generating electricity

Most of those cases are energy crops planted in areas with restrictions for the species used. A clear case in Miscanthus, a C4 (four carbon methabolic photosynthesis) tropical “warm” grass in northern Europe or North America.  Other cases are semiarid lands with short rotation coppice using willow or even poplars. In Spain, to give another clear example, irrigation costs in Southern areas would require about 1200 €/ha per year only for rental land and about 1000€/ha to irrigate the crop since drought and arid conditions occur during almost all spring and summer months. Even with high productivity during the lifespan (often 16 years in SRC in Spain and average yields between 14 to 25 odt/ha per year) , most demonstration plots and commercial plantations have shown costs between 70 and 120 €/odt (90 to 140 U$D/odt). Why not trying something else? Why not promoting drought tolerant species with lower yields? Our experience shows that several alternative are feasible and might have lower delivered cost even considering high logistics costs to collect a more disperse biomass in the field.

Might lower cost per hectare in marginal lands determine lower inputs and delivered biomass costs per ton in the gate of our facilities?

A good example for all this is also what is happening right now with Miscanthus in marginal soils or colder areas where annual average yields during the lifespan of the crop are often below 10 odt/ha. High rhizome planting costs for establishment and low productive areas make the crop provide high biomass production costs. A grassland and several energy crops with lower costs (like Switchgrass and many C3 energy grasses with drought and frost tolerance could be easily better options).

The establishment cost of some energy crops can be as high as 5000 U$D per hectare. High yields in fertile and productive lands are needed in these cases. Therefore, those “high input” crops should be considered to be introduced in rotation with benefits in more fertile and productive areas where food production is also feasible and perennial crops or short rotation coppice might be beneficial for soils.

The case of giant reed (Arundo donax) is similar in semiarid conditions. Productivity can be as high as 45 odt/ha per year as many projects have been showing. The yield curve and lifespan is not really well described but the fact is that when yields are low, costs will be really high. Our experience in irrigated semiarid lands also showed feedstock costs to be higher than 90 U$D/odt. We normally consider to remove and eradicate the plantation after lifetime finish (with additional  costs certainly).

Perennial crops are often mentioned as most feasible options to provide environmental benefits and low costs for biomass.  Sorghum ,winter annual grasses and maize have shown truly high costs in areas with yields between 10 to 20 odt/ha. Higher yields require better soils and climate conditions to reach breakeven  points. Annual productivity in semiarid regions, extremely cold and warm areas or saline soils is often lower considering soil fertility and climate restrictions.

Organic matter increases when introducing rotations in semiarid lands. Most annual cash crops for food production increase yields and require lower fertilizer rates after a 10 years with perennial grasses or shrubs.

Marginal areas have been a focus of attention these years since governments require policy to provide green covers, rural income, diversify risk in degraded areas with agricultural and climate risks. Additionally, marginal lands have often lower competitiveness for agriculture and food production so bioenergy would be more interesting and have no food crop/prices disruption effects. While biomass costs in northern regions of Europe and US  often oscillate from 15 to 60 U$D per oven dried ton (odt), most energy crops like Miscanthus or short rotation coppice provide often higher production costs for biomass at the farm level (60-130 U$D/odt). Same happens sometime with highly productive crops like giant king grass from Viaspace (Pennisetum purpureum) and other tall grasses and trees like Paulownia that require often rhizome planting or nurseries to propagate planting materials.

But we know also that those areas are limited and would extract lower nutrients as produced biomass and carbon/nitrogen exports are surely lower. Shrubs, forestry and grasslands could be all possible alternatives to cover with vegetation extensive areas avoiding desertification.  But lower yields would require high efficiency to convert biomass into energy. What technologies and what crops are both considerable questions to discuss. 

CAM plants can provide low yields but high energy balances and huge emission savings providing lignocellulosic materials with potential use for bioenergy

Marginal areas have lower yields but they certainly have lower production costs such as often lower cost of land, water and even personnel. Larger scale also can play an important role lowering costs. Huge extensions allow  lower management costs for cultivating and input management. The lack of opportunity costs allow a low production cost that many times can be lower compared to other more used  feedstock (residues and dedicated “taller” energy crops). 

So now we are talking on lower yields (odt/ha per year) but also having lower costs in terms of $/ton.

What are logistic implications: improvement and cost reduction is required

A critical aspect of course, is that in marginal areas with lower yields, a company will require much more surface and improved logistic chains should be required. We often studied the fact and offer several solutions compacting biomass, reducing moisture and decentralizing operations. Grass cuttings for any green cover (such as grasslands) range from 15 to 30 U$D / odt depending on equipment used. Baling shurb and woody materials or even mixes with grasses  or any other feedstock  is not a limiting factor if  proper equipment is considered. Some advice and consulting with several possible solutions for specific conditions should be studied. From compaction and big balers to accumulators and cleaning in central processing facilities in the field are realistic options to consider. Additionally, pelletizing biomass from grassland might be feasible and have acceptable costs reducing transportation and handling costs in some cases.  A good  example  from the United States Department of Agriculture (USDA) can be found here. That can be also applied to other several feedstock even better adapted for marginal and semiarid lands.

What biomass to energy processing technologies should be considered when yields are lower?

1st generation biofuels have lower energy balances and emission savings replacing  fuels and  are now  under debate as many feedstock have been showing low performance in particular in marginal lands. Other technologies instead could provide more accurate results with higher efficiency levels. Heat and electricity as well as biogas and second generation biofuels could be produced from feedstock. Residues have been used in last decade to produce biopower and more facilities for biopower and 2nd generation bioethanol are being opened every year as EIA report (2013) has shown some weeks ago (check ir here). The same documents foreseen a expansion on lignocellulosic crops in next decades.

Marginal lands require low inputs and energy crops that allow farmers to have more options to reduce the higher cost their areas have. Biodiversity benefits are also a good reasons to avoid high inputs in marginal lands

Environmental aspects of producing feedstock in marginal lands:

Producing energy crops in arable lands is already a reality in several countries. Many options today consider perennial grasses because of their implications regarding environmental issues such as carbon cycle, organic matter, erosion control, biodiversity, groundwater impacts and nutrient leaching. As much as researchers concern, the trend today is on lignocellulosic perennial species to avoid impacts and produce higher benefits.

Rotations with perennials in marginal lands are other relevant discussion here. Mono-culture system with cereals in semiarid lands are today deteriorating soils and produce a not sustainable production system with high inputs even producing food. In Europe for instance, livestock policies determined in last decades a low possibility for grasslands and perennial species. Rotating with perennial species for energy purposes open a new market while introducing  fallow lands in the agricultural current management. Rural income and employment opportunities allow a more sustainable pattern combining and integrating bioenergy crops with food annual crops. The effect of 10 years rotation of perennial species on arable lands and cereal or oil crop yields  is already very well documented.

Other important issue is how possible would be to re-establish an energy crop with minimum tillage and input requirement. Grasslands and several other energy crops can be re-established easily without the need of new cultivation and land preparation operations. Pasture renovations and shrub or native forest management are all well studied options to produce low yields with minimum inputs and have a longer lifespan for energy crop production. If nutrient extraction   levels are considered, a system with 5-10 odt/ha per year would be easily managed to produce a good green covered land with successive harvest for long periods (8-30 years). Cardoon, Switchgrass and Tall wheatgrass as all good examples of energy crops for marginal lands that might be follow this aspect re-establishing the crop with non-tillage management (direct sowing).

Here we present 7 crops with enough evidence and often lower costs to produce biomass. In our experience, a grassland with suited management techniques or even some shrubs and dedicated energy woody crops and short rotation coppice are all viable options in semiarid lands, in colder areas or extremely dry zones. In our experience, producing biomass from marginal lands with energy crops can have production costs of 15-50 U$D per ODT in many areas of the world.

Energy and agricultural policies should consider what we can do in those areas while fossil energy prices continues to rise and mono-cultures occupy so many areas.

So, how socially, environmentally and economically feasible could all this be? We think that energy crops in marginal lands could be an option providing the following results:

• Lower Feedstock costs (15-65 U$D / odt).
• More green covers and environmental benefits.
• Reforestation schemes with huge potential in many areas of the world
• Reduction in risks for supply as more options are viable for those areas.
• Less mono-culture and more rotations improving organic matter with potential benefits for food cropping systems (subsequent food crop yields in many cases are higher after a rotation with 6-10 years of a perennial)
• Increases in biodiversity as more perennial species are possible even combining grasses, shrubs, short rotation coppice and agro-forestry alternatives.
• New services, more companies and more local renewable energy in poor regions.
• Rural employment in rural areas as more crops and more lands would have a market.