Research leading to improved crops for use in livestock systems offers a uniquely valuable viewpoint on the current hot topic of bioenergy.

A most important first lesson from this perspective is to stop using the narrow terms bioenergy or biofuel or biodiesel, and to think of plant biomass as much more than firewood.  The issue is a broader one of biorenewables.

Why?  Because nuclear power, or solar panels, or wind turbines, or wave machines or barrages may help replace fossil sources of energy; but they have nothing to contribute to meeting the continuing need for petrochemicals.

The lesson from the livestock production chain is: control your waste stream or your system is unsustainable (think BSE, Cryptosporidium, slurry, nitrates legislation, animal welfare…).  The parallel with the biorenewables pathway is clear, and the key is to think in terms of the biorefinery.

The biorefinery concept moves beyond the current first-generation bioenergy strategy, with its crazy dependence on food crops, and even beyond second-generation biomass-based energy cropping.

Biorefinery in this sense is an exact parallel to the livestock-based system.  But instead of a fermenter that goes “moo” and converts biomass into steaks and milk, it’s made of stainless steel and fractionates the crop into energy products and chemical feedstocks.

Basically, we’re talking about a factory-scale rumen.

It may even turn out that forages bred and managed for efficient ruminant livestock production are right for biorefinery.  This would have lots of good consequences.

Farmers already know how to grow the stuff and have the technology to collect it.  Existing distribution chains and processing infrastructure (for example milk collection and regional dairy plants) could be adapted without too much trouble for biorefinery.

This could be done without changing rural landscape and culture.  Moreover, the Greens keep telling us we produce and consume too much meat and dairy for the planet to cope; this is a gentler way of converting from livestock agriculture than militant vegetarianism.

Click here for a schematic of the sequence from biological solar energy capture through to bioenergy and organic feedstocks and fine chemicals, showing where effort in research and development needs to be directed.

Before biorenewables can be turned from a concept and an empirically-based cottage industry into practical reality, we need to understand and to be able to control biomass yield, quality and sustainability.

This means delving into issues like the efficiency of biomass production and processing, the exploitable chemicals present in biomass and the impacts of these chemicals on downstream processing and the environment.

There’s plenty of scope for the fundamental and applied genetics of biomass species to make decisive interventions.  For example, traditionally there has been little or no breeding directed at improvement of crops grown for thermal conversion such as poplar, willow, Miscanthus, reed canary grass and switch grass (but this is changing fast – click on the links).

Biorefining these species, and the food and feed crops currently going into first-generation biofuel production, will require R&D directed at optimising the important quality traits, namely lignin, cell wall cross-linking phenolics and carbohydrate content.

Most of the first-generation biofuel crops are annuals – cereals, oilseed species.  But the future belongs to perennials.

Why?  Because they require no tillage (which is energy-intensive and also releases CO₂ from soil), they need relatively little fertiliser, they efficiently relocate nutrients from shoot biomass to the roots, they tend to be resistant to environmental stresses like drought and disease and they generally thrive on lower quality land than arable crops.

The pictures on the right show Miscanthus.  Senescence, dry-down and nutrient return to the below-ground rhizomes are necessary to produce low-moisture, low-mineral, high-quality biomass without repeated tillage and fertiliser application.

So we need to improve our understanding of perenniality, resource partitioning and nutrient cycling to make full use of these species.  This means more research is needed on flowering, senescence (of course!), carbohydrate metabolism, N storage and remobilisation in rhizomes.

Half of the CO₂ fixed in the biosphere ends up in plant cell walls.  Alongside the promise of perennials, there is prospect of being able to unlock the potential of cell wall lignocellulose as a carbon source.

The nature of the cell wall largely determines biomass quality.  For high calorific value (combustion) it needs to be highly cross-linked; for bioconversion low cross-linking is required.

To improve the perennial lignocellulose biorenewable crops, all the tools of modern plant breeding and technology will have to be applied, including the development of genetic resources, high-throughput screening methods and molecular markers.