From food debate and land use changes effects to biofuels sustainability, a lot of scientific findings show great differences among alternatives. We joined best scientific information. The food debate and several critics to biofuels have been addressed recently. We debate on biomass energy viability and sustainability criteria and food security but we know there are great differences depending on alternatives. Not all biomass and bioenergy cropping systems and processing technologies have same performance and achieve sustainability standards.
When analyzing bioenergy systems one need to focus attention in the following aspects:
- Land use and food crops that could be displaced. Feasibility in low competitive, not used and marginal lands is a key issue
- Energy balance: Energy output (in Megajoules per hectare) minus energy input (megajoules used).
- Energy ratio (Energy output / energy input) in %
- Emissions savings compared to the replace fuel or currently fossil energy used
But how much marginal lands we have? Well, most studies conducted give number of hectares ranging from 600 to 1100 million hectares globally. That often considers only lands with potential for biofuels and have not always considered reforestation with short rotation coppice or grasses / grasslands that today are well document feedstock possibilities for bioenergy production.
Here we have included most relevant scientific evidence pubished mostly during last decade.
A) Bioethanol from cereals, sugar and starch crops
Most evidence shows that 1st generation biofuels obtained from corn have a very low energy balance when considering fossil energy used to produce a liter of ethanol. However, using corn-stover and residues for heat/power alternatives as well as biogas, may help. Additionally, sugarbeet, sweet sorghum and cassava have been showing better performance compared to corn when producing first generation bioethanol. Converting grasslands and lands with perennial species for annual arable crops producing feedstock for bioenergy can be detrimental and reduce carbon stock as evidence outlines.
If biomass produced is used mostly for bioethanol production, energy balances and emissions savings are not that high compared to fossil fuels replaced. Using heat and power from solid biomass resources in the processing can significantly improve biofuel performance, emission savings and energy balances.
Here some sound publications.:
- Reducing life cycle greenhouse gas emissions of corn ethanol by integrating biomass to produce heat and power at ethanol plants
- Estimating life cycle greenhouse gas emissions from corn–ethanol: a critical review of current U.S. practices
- No-tillage conversion of harvested perennial grassland to annual cropland reduces root biomass, decreases active carbon stocks, and impacts soil biota
- Energy consumption and GHG emissions of six biofuel pathways by LCA in (the) People’s Republic of China
- Energy and greenhouse gas balances of cassava-based ethanol
- Effect of biogas utilization and plant co-location on life-cycle greenhouse gas emissions of cassava ethanol production
- Energy use indicators in energy and life cycle assessments of biofuels: review and recommendations
- Greenhouse gas footprints of different biofuel production systems
- Optimization and analysis of a bioethanol agro-industrial system from sweet sorghum
- Biorefinery of sweet sorghum stem
- Energy and greenhouse gas emission effects of corn and cellulosic ethanol with technology improvements and land use changes
B) Biodiesel from annual oil crops and oil-trees
The production of biodiesel is well known worldwide. However it is completely different to produce soybean as “second-crop” in certain regions (e.g. Argentina) with non-tillage methods in the same hectare that has produced wheat for food. Additionally, costs, emissions, and energy yields change drammatically if by-products are used or not. Rapeseeds in EU and palm oil in Indonesia have been showing different performance too. The following information and publications show clearly that by-products and sinergies with heat/power applications can improve life cycle assessments when producing biofuels from these alternatives. Additionally, it is very much evident that oil trees would be the only way to maximize environmental benefits producing biodiesel in marginal lands without food disruption and major land use effects.
Unfortunately, most oil trees have still to be developed commercially. Even in Jatropha curcas, Moringa and other trees performance is promising, we see that only certain cases can scale-up the production level in marginal areas. Some publications with that information can be found here below:
- Large-scale bioenergy production from soybeans and switchgrass in Argentina
- Soy biodiesel pathways: Global prospects
- Biodiesel CO2 emissions: A comparison with the main fuels in the Brazilian market
- Biodiesel production and comparison of emissions of a DI diesel engine fueled by biodiesel–diesel and canola oil–diesel blends at high idling operations
- Regional life cycle assessment of soybean derived biodiesel for transportation fleets
- Net energy balance of small-scale on-farm biodiesel production from canola and soybean
- Biodiesel production from mixed soybean oil and rapeseed oil
- Comparison of palm oil, Jatropha curcas and Calophyllum inophyllum for biodiesel: A review
- A review of biodiesel production from Jatropha curcas L. oil
- A review on prospect of Jatropha curcas for biodiesel in Indonesia
- Life cycle cost and sensitivity analysis of palm biodiesel production
- Global greenhouse gas implications of land conversion to biofuel crop cultivation in arid and semi-arid lands – Lessons learned from Jatropha
- Life cycle assessment of Jatropha biodiesel as transportation fuel in rural India
- Assessment of the biomass energy potentials and environmental benefits of Jatropha curcas L. in Southwest China
- Assessment of Jatropha Curcas bioprocess for fuel production using LCA and CAPE
- A comprehensive life cycle assessment (LCA) of Jatropha biodiesel production in India
- Combustion and performance of a diesel engine with preheated Jatropha curcas oil using waste heat from exhaust gas
- An introduction to the life cycle assessment (LCA) of bioelectrochemical systems (BES) for sustainable energy and product generation: Relevance and key aspects
C) Heat and power from combustion, cogeneration and gasification are in general more efficient than first generation liquid biofuels.
Comparing energy balances, emissions savings and environmental impacts in different bioenergy pathways take directly to the same conclusion: solid biomass producing heat and power is a much more convenient way to produce energy from biomass. In the following publications it is possible to find relevant evidence regarding emission savings when replacing fossil fuel, power or heat with biomass sources.
Many technologies include combined heat and power, direct combustion in improved steam boilers, gasification and pyrolisis and many others.
- Greenhouse gas and energy analysis of substitute natural gas from biomass for space heat
- Land use changes, greenhouse gas emissions and fossil fuel substitution of biofuels compared to bioelectricity production for electric cars in Austria
- Design improvements and performance testing of a biomass gasifier based electric power generation system
- Energy balances and greenhouse gas-mitigation potentials of bioenergy cropping systems (Miscanthus, rapeseed, and maize) based on farming conditions in Western Germany
- Cost-effective CO2 emission reduction through heat, power and biofuel production from woody biomass: A spatially explicit comparison of conversion technologies
- Energy- and greenhouse gas-based LCA of biofuel and bioenergy systems: Key issues, ranges and recommendations
- CHP or Biofuel Production in Europe?
- Co-generation of biofuels for transportation and heat for district heating systems—an assessment of the national possibilities in the EU
- Greenhouse gas balances of transportation biofuels, electricity and heat generation in Finland—Dealing with the uncertainties
- Carbon and energy balance from a range of biofuel alternatives (heat, power and biofuels considered)
D) Lignocellulosic energy crops for Second Generation Bioethanol
Several highly reputed peer-reviewed scientific journals (Biomass & Bioenergy, Applied Energy, Energy Policy and others) have been showing that lignocellulosic raw materials from crops can produce great advatanges in terms of second generation bioethanol production. However, commercial demonstration and up-scaling is still a problem in mosst countries. In the following section we show some great publications to consider as well as annual reports from relevant organizations such as the International Energy Agency.
- Progress in the production and application of n-butanol as a biofuel
- EIA: Annual energy outlook 2013
- How to ensure greenhouse gas emission reductions by increasing the use of biofuels? – Suitability of the European Union sustainability criteria
- Optimizing on-farm pretreatment of perennial grasses for fuel ethanol production
- Bioethanol from lignocellulosics: Status and perspectives in Canada
- The environmental and economic sustainability of potential bioethanol from willow in the UK
- Cradle-to-farm gate life cycle assessment in perennial energy crops
- Production of bioethanol from lignocellulosic materials via the biochemical pathway: A review
- LCA of second generation bioethanol: A review and some issues to be resolved for good LCA practice
- An analysis of net energy production and feedstock availability for biobutanol and bioethanol
E) Lignocellulosic energy crops for heat and power: biomass from perennial species in marginal lands
In Europe, most viable alternatives today are perennial grasses and short rotation coppice to produce lignocellulosic materials. This has a tremendous significance since tropical and subtropical areas as well as large territories in North America, South America, Africa and Asia have potential to implement large scale projects in low competitive areas for traditional agriculture and livestock production. Degraded areas, marginal lands with low possible development for grazing or food prodcution are being considered. Those areas can offer a meaningful potential for afforestation / reforestation schemes where biomass can be valorized at the time a “greener” landscape is achieved. Here some good information about it:
- Land Availability for Biofuel Production
- The development and current status of perennial rhizomatous grasses as energy crops in the US and Europe
- Biomass yield and energy balance of a short-rotation poplar coppice with multiple clones on degraded land during 16 years
- Comparative economic analysis of perennial, annual, and intercrops for biomass production
- Investigating the effectiveness of environmental assessment of land use change: A comparative study of the approaches taken to perennial biomass crop planting in São Paulo and England
- Comparing annual and perennial energy cropping systems with different management intensities
- Effects of heating rate and water leaching of perennial energy crops on pyrolysis characteristics and kinetics
- Hybrid poplar growth in bioenergy production systems: Biomass prediction with a simple process-based model (3PG)
- Assessment of bioenergy potential on marginal land in China
- Strengths, Weaknessness, Opportunities and Threats Analysis of Bioenergy Production on Marginal Land
- Total and available soil carbon fractions under the perennial grass Cynodon dactylon (L.) Pers and the bioenergy crop Arundo donax L.
- Worldwide commercial development of bioenergy with a focus on energy crop-based projects
To see more about grasses, perennials and energy crops please refer to this link.
F) Energy crops for biogas
We already have a good post with most references here. Additionally, you can see recent publications as follows:
- Energy balances for biogas and solid biofuel production from industrial hemp
- Energy crops for biogas. A handbook.
- Biogas production from energy crops and crop residues
- Biogas from Energy Crop Digestion
- Biogas from energy crops and biowastes
- Biogas production from energy crops and crop residues
- Evaluation of Energy Crops for Biogas Production with a Combination of Simulation Modeling and Dex-i Multicriteria Method
- Biogas From Energy Crop Digestion
- Economical Viability of Biogas Production from Energy Crops
- Present and Future of the Biogas in Spain
- Energy balance and cost-benefit analysis of biogas production from perennial energy crops pretreated by wet oxidation
- A Multi-Criteria Assessment of Energy Crops for Biogas Production
- Swedish resource potential from residues and energy crops to enhance biogas generation
G) Combinations between energy crops, residues and different technologies.
Most combined systems have increments in sinergies that determine much large environmental benefit, reduce land use effects and improve energy efficiency during conversions. That’s why several researchers and companies are focusing in the biorefinery concept.
In many sugarcane mills, coffe factories, sawmill and other biobased industries, residues available are a main barrier for higher efficiency levels. Boilers size and large scaling potential is often limited to residues available in the main industry. Typically, a sugarmill starts with its bagasse but that serves to a certain level of energy output (lets say, 10MW). A higher plant of course will determine a higher efficiency. Thus, more feedstock would be needed to produce in a more efficient way. Cropping marginal areas for sugarcane is a way out. Similarly, a forestry mill will require to reforestate or promote afforestation.
Some good examples of recent scientific publications with great advatanges and demosntration are here:
- Bagasse combustion in sugar mills, process description from Environmental Protection Agency
- Biorefineries for biofuel upgrading: A critical review
- Biorefining of perennial grasses: A potential sustainable option for Northern Ireland grassland production
- Cropping bioenergy and biomaterials in marginal land: The added value of the biorefinery concept
- Process synthesis of hybrid coal, biomass, and natural gas to liquids via Fischer–Tropsch synthesis, ZSM-5 catalytic conversion, methanol synthesis, methanol-to-gasoline, and methanol-to-olefins/distillate technologies
Some examples of residues and dedicated plantations that determine benefits are included in the following sections:
- Brazilian sugarcane bagasse: Energy and non-energy consumption
- Electricity generation from eucalyptus and bagasse by sugar mills in Nicaragua: A comparison with fuel oil electricity generation on the basis of costs, macro-economic impacts and environmental emissions
- The Economic Impacts of Bioenergy Crop Production on U.S. Agriculture
- Mixed sugarcane and elephant grass silages with or without bacterial inoculant
- Bagasse pellets: how Brazilians plan to create a market
- Downdraft gasification of pellets made of wood, palm-oil residues respective bagasse: Experimental study
- Pyrolysis and gasification of pellets from sugar cane bagasse and wood
- Trigeneration in a northern Chinese village using crop residues
H) Negative solutions and energy crops: the case of pyrolisis and biochar with biomass from energy crops
Several studies have been focusing on biochar as a residue that can allow negative carbon sequestration. Using biomass from energy crops makes possible to use gasifiers and pyrolisis technologies that offer a solid residue that can be used to improve soils (organic matter and pH amendment). This has enough evidence to produce sustainable advantages when bioenergy crops are considered to improve food arable lands (e.g. horticultural areas, etc.).
Here some sound scientific publications to be considered:
- Prospective life cycle carbon abatement for pyrolysis biochar systems in the UK
- Pyrolysis biochar systems for recovering biodegradable materials: A life cycle carbon assessment
- Life cycle assessment of biochar cofiring with coal
- Benefit assessment of cost, energy, and environment for biomass pyrolysis oil
- Biochar—One way forward for soil carbon in offset mechanisms in Africa?
- Environmental assessment of gasification technology for biomass conversion to energy in comparison with other alternatives: the case of wheat straw
- Influence of production conditions on the yield and environmental stability of biochar
- Comparing energy balances, greenhouse gas balances and biodiversity impacts of contrasting farming systems with alternative land uses
- Negative carbon intensity of renewable energy technologies involving biomass or carbon dioxide as inputs
I) Integration of alternative feedstock from dedicated energy plantations and sinergies with food production
It is a well documented aspect the fact that using residues from food and forestry industries (or even urban residues) can be completed with biomass obtained from lignocellulosic woody and herbaceous energy crops. In the following section we included several publications that bring strong evidence about this issue.
Using food wastes from vineyards, olive trees, coffe, mango, citrus and several other agri-industries, can be combined with energy plantations, hedgerows, agro-forestry and produce lignocellulosic materials for heat/power to be offered to the grid. All environmental performances are 100% different from any other alternative considered in this document as the combinations are infinite.
This issue, is a critical point when determining land use changes effects of bioenergy environmental performance since energy and emissions allocated to final products can largely modify analysis of results and final conclusions on sustainability of these alternatives.
Evidences on this can be found here:
- Agroforestry systems for the production of woody biomass for energy transformation purposes
- Biomass production in agroforestry and forestry systems on salt-affected soils in South Asia: Exploration of the GHG balance and economic performance of three case studies
- Quantification of the residual biomass obtained from pruning of vineyards in Mediterranean area
- Analysis of olive grove residual biomass potential for electric and thermal energy generation in Andalusia (Spain)
- Solar-dried citrus pulp as an alternative energy source in lamb diets: Effects on growth and carcass and meat quality
- The global potential for Agave as a biofuel feedstock
- Land disposal of municipal effluents: importance of choosing agroforestry systems
- Land use for integrated systems: A bioenergy perspective
- Roll press compaction of corn stover and perennial grasses to increase bulk density
- Some ecological and socio-economic considerations for biomass energy crop production
- Is energy cropping in Europe compatible with biodiversity? – Opportunities and threats to biodiversity from land-based production of biomass for bioenergy purposes
- Sustainable biomass production for energy in the Philippines
- Biomass energy of rice drying
- A review on utilisation of biomass from rice industry as a source of renewable energy
- Energy potentials and sustainability—the case of sisal residues in Tanzania