Bioenergy Crops Biofuels sustainability: Not all alternatives are the same.

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

Sugarbeet may produce high amounts of ethanol but it mostly requires high inputs and fertile lands or even irrigation. Photo: Syngenta

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.:

B) Biodiesel from annual oil crops and oil-trees

jatropha curcas was considered first as a great promise for deserts and semiarid lands and today is mostly cultivated in more fertile lands. Using solid wastes can improve the environmental performance and energy balances. Photo: Martha Avila taken from http://pulsoverde.nrdc.org/

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:

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.

D) Lignocellulosic energy crops for Second Generation Bioethanol

Farmer cutting warm grasses in the tropics. Picture from © – FLPA/Wayne Hutchinson

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.

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:

Virginia fanpetals. This unique species, when harvested in the dry stage, has applications in the bioenergy, insulation and cellulose-paper industries.

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:

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:

Some examples of residues and dedicated plantations that determine benefits are included in the following sections:

H) Negative solutions and energy crops: the case of pyrolisis and biochar with biomass from energy crops

Biomass + Pyrolysis = Biochar + Thermal Energy. Photo: greaterdemocracy.org

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:

I) Integration of alternative feedstock from dedicated energy plantations and sinergies with food production

Burning wastes in a destilleryhas been enough demonstrated. Biomass introduced can be completed with energy crops to increase feedstock availability and efficiency. Photo: Whisky Pot Stills at the Glendronach Distillery Akela NDE via Wikimedia

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.

Agroforestry in tropical areas allow grazing and woody crops to avoid deforestation and produce energy and food from same lands. Photo: Leucaena trees and guinea grass in tropical lands. Photo: tropicalforages.info

Evidences on this can be found here: