An Unlikely Renewable Bottleneck: Machines to Harvest Weeds

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We are at a point in history when innovations are needed rivaling those of the information technology industry in speed of change – for the development of farm machinery for growing and harvesting new crops that produce energy.

Machinery suitable for growing and harvesting traditional crops have been developed, and refined, and ultimately, mechanized, over centuries. Now we have to find a way to grow biofuels, on land that’s not needed to grow food, and in a way that is economical, and massively replicable.

Currently only a handful of companies are working on the novel problem, among them, according to Craig Patterson, Manager of Commercial Operations there, Repreve Renewables.

Here’s an example of an issue they are trying to solve. Miscanthus holds great promise as a non-food, non-valuable-land biofuel, as it is a virtually a weed in the Midwest and Southeast, and can produce up to 20 tons an acre, far more than switchgrass.

The problem with it is that it can be hard to establish on a commercial basis. Although it is a weed that sews its own expansion, it does it haphazardly.

If you want to “farm” it in a way that lends itself to efficient energy crop production, you need to reproduce it from actual pieces of the underground plant system (from cuttings called rhizomes) that must be dug up and replanted, at the rate of around 5,000 rhizomes to the acre.

The speed and cost of planting, it turns out, is a real bottleneck in viability of this crop as a successful feedstock. Current planting technology can plant, at best, 20 acres per day.

A typical biorefinery needs at least 3,000 acres of crop to run efficiently, he says, but that 3,000 acres would take 150 days to plant, this way. By the time planting was done, the planting season would be long over.

“Putting five pieces of equipment on site reduces the planting to 30 days,” says Patterson.”But imagine that the planting is going on in five different states, on 15 different farms.  Suddenly you need 75 teams planting all at once, across several states. In this scenario, 45,000 acres – a drop in the bucket of what is required – would require millions of dollars of equipment and labor to achieve. And that is a bottleneck”.

That’s where inventive farm machinery comes in. Repreve Renewables is one of just a handfull of companies developing machinery for the task.

Strange times. After 10,000 years of agriculture, with generations of inventors devising ways to battle weeds, in the 21st century we need to invent machinery to do a more efficient job of harvesting them.

Image: Newswise
Susan Kraemer@Twitter

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