The Cooperative Research and Development Agreement (CRADA) between NREL and Ecopetrol aims to improve the conversion process for bagasse (the material left over after the sugars are removed from the sugar cane) and to analyse the economic potential of commercial production of biofuel from these materials. The CRADA will also include some limited study on palm rachis – the material left over after palm oil production.
The US$2.3 million 18-month project is being funded by Ecopetrol, which is using NREL for its expertise on conversion of biomass, its compositional analysis and techno-economic analysis capabilities, and facilities. NREL has a pilot plant at its Golden, Colorado campus that has conversion capabilities from lab scale to pilot scale, processing up to one ton per day of biomass – everything from corn stover to switchgrass and poplar trees.
Colombia has an abundance of biomass in the form of sugar cane. The rainfall patterns in the region near the Pacific Coast where the sugar is grown for the biofuels industry allows the crop to be harvested all year round, but there's not much room for expansion.
Sugar cane also is grown farther east, but because of incessant rain from April to August, it can only be harvested eight months a year. The plant spoils quickly if the sugars aren't squeezed out. But the bagasse – the leftovers that comprise a majority of the plants' mass and give it rigidity and structure – can be stacked and stored for a long time after the juice is removed and washed out of the green grass stalk.
That bagasse currently is burned to produce steam that drives turbines for electricity, but Ecopetrol is hoping to get more value out of it than that.
The hope is that commercial conversion facilities and employees can be kept busy all year round by processing the bagasse during the rainy season when it's too wet to get to the fields and harvest the sugar cane. It's more challenging to break down the cellulose in the bagasse than the sugar-rich juice, but if the conversion process is successful, the bagasse can be processed into a biofuel.
Ecopetrol already has in place a commercial facility for converting sugarcane juice into fuel-grade ethanol. The fermentation and distillation equipment at that facility could also be used to hydrolyse the bagasse and ferment the resulting sugar into additional ethanol, increasing the output of the facility and enabling year-round operations. It would only have to add the pretreatment process and tweak the ‘knobs and dials’ to optimise the operation, according to Rick Elander, biochemical conversion manager at NREL's National Bioenergy Center. NREL already has experience in breaking down feedstock so it's ready for enzymes. "Nature makes it much more difficult to break those bonds that give the plant rigidity and strength," said Elander. "But we know how to liberate those sugars and we're working on doing it as quickly and cheaply as we can.
"This can be a great opportunity to leverage off infrastructure that's already bought and paid for, which would otherwise be sitting there idle," he added. "It will take a little additional investment by Ecopetrol on the front end.
"We're going to help them figure out if the performance they're getting from the available lignocellulosic feedstocks is going to make economic sense," Elander said. "On paper, you could make a pretty good case for it because they're not starting from scratch. They have a facility and infrastructure in place and they have that captive bagasse feedstock that is already at the facility."