Scion Biofuel Research

New Zealand has an opportunity to reduce its reliance on imported transport fuels by around 60%. It would involve doubling the area currently planted in forest to provide enough woody raw material for biofuel production. The additional forests could be grown on marginal land too steep or poor to graze or otherwise use productively. Establishing such forests would stabilise land reducing runoff and erosion, provide local employment and could give a net gain to the economy of around $4.8 billion per year through import substitution.

This is one of the conclusions reached by the Bioenergy Options for New Zealand project led by Scion. Forest wood and wastes are the largest renewable source of bioenergy feedstock that New Zealand has the ability to grow in massive quantities without reducing food or feed production.

Scion is now in the middle of a three year project looking at ways of converting wood from radiata pine into sugar that can in turn be converted into ethanol. The sugar-to-ethanol step is well established and that technology can be bolted on once the wood-to-sugar step is sorted out. One of the problems is that pine wood contains significant amounts of lignin which interferes with the enzymatic digestion of wood carbohydrates. The research challenge is to treat the wood so that the enzymes can still work and to also recover the lignin so it can be burnt to produce the heat needed in the process or use it as a feedstock for bioplastics.

Scion has been able to accomplish this in the laboratory and is now evaluating the procedures on a pilot scale plant. The aim is to produce enough sugar and lignin material for evaluation overseas by biofuel and bioplastics manufacturers.

The lignocellulosic bioethanol initiative:

The FORST funded research program is about 60% through. It is aimed at enabling the production of ethanol, and other biofuels such as biobutanol, from softwood such as radiata pine grown in New Zealand. The process requires material that contains carbohydrates, particularly cellulose and hemicelluloses. This means wood, not bark. Pine is the feedstock of choice because there is much already available and because Pinus radiata grows like a weed throughout the country.

However, softwoods such as radiata pine have proved the most difficult to convert to biofuels because of their chemical make up and physical structures. They are quite high in lignin, which is a problem because it can inhibit the enzymes that break down the cellulose and hemicelluloses to sugar. The research challenge is to treat the wood in a way that the enzymes can still break down the carbohydrates, even in the presence of the lignin. Some processes use sulphuric acid which is effective but produces a lignin which is only suitable for burning. Dr Ian Suckling, technical leader of the biofuels programme, says that they have worked out a process that maintains the value of lignin and is technically successful.

We take woodchips, for example, and do a treatment involving heat and mechanical action that breaks them down into a form that can then be treated with enzymes. The enzymes break the cellulose and hemicelluloses down to glucose and other sugars, and the end product of the process is a solution containing sugars such as glucose plus an insoluble residue that has lignin in it, he says.

So we have a potentially very good process for converting softwoods but we still to get costs down to make it viable. That requires further technical innovation, for example, one of the targets is to minimise the amount of enzyme used.

Lignin is the cement that keeps the cellulose fibres together, poses a problem in that it can reduce enzyme activity, but it also has value. In most biofuel plants it is burnt to produce processing energy needed to distil off ethanol. However, Ian points out that is has potentially higher value.

Our process produces a particularly valuable lignin that could potentially be converted to other products such as bioplastics, and Scion has other research projects under way to look at this, he says.

Our program stops at the wood sugar because the technical gap is in that part of the process. There is a huge amount of international activity in this area, particularly in the USA, but not that much on softwoods. The technology for converting the wood sugar to biofuel is well established and is not dissimilar to beer making fermentation and then distilling off the ethanol.

When we have demonstrated all the key steps at pilot scale the next stage will be to scale the process up further, but that will likely be someone elses job. Each time you scale up you run into new challenges and you have to resolve them before you invest in a full-scale plant.

Scion managed a government funded program to determine where in New Zealand the best feedstocks for bioenergy are, and concluded that the only major feedstock was forest biomass. They calculated that if the current forest estate was doubled ie. another 1.8 million hectares, developing technologies could replace 65% of all fossil transport fuels in New Zealand. The net benefits in would be about $5 billion a year in carbon and import offsets. Dr Trevor Stuthridge, Group Manager - Sustainable Design at Scion, says planting about 74,000 ha of forest per year for the next 25 years would sustain that level of fuel replacement and achieve offsets against fossil fuels of around 11 million tonnes per year.

The forest would be grown differently because we would not be concerned about whether it would make good paper or timber. More trees would be planted per hectare, and they would be harvested between 10 and 15 years when the bulk of the carbon storage has occurred, he says.

We may also consider using different types of trees, choosing them on the basis of their growth rate and capacity to store carbon rather than density and by the strength as at present. We are looking at other species but Pinus radiata is a fabulous weed that grows almost anywhere in New Zealand.

New forest on marginal land is proposed, and to solve problems of infrastructure they are looking at distributed processing where a small plant would be taken out into the forest to do the initial processing and drying of material (wood is about 80% water).

We have done calculations on costs, and the optimum size of plant based on the available residues is about 90,000,000 L per year. That would mean about 80 plants of that size around the country, says Trevor.

We see opportunities for marginal lands and for distributed energy biomass processing, and in the coming year we will be looking at the viability of having smaller processing facilities at the plantation forests. It might be that smaller forest owners and farmers form a cooperative and support distributed biomass processing facilities, or it could be amongst iwi who have marginal land with forest already on it or want to establish more forest and are looking for local economic drivers.

So rather than shipping the raw material straight off site, they would add value on-site in their region and get the social benefits of employment etc around distributed energy processors. This is what happened in the US where the corn ethanol industry had groups of farmers getting together and investing in corn ethanol plants locally. It seems a reasonable proposition here.