Summary & Background
A cradle to gate GHG assessment was carried out in 2016 to UK standard PAS2050:2011. The study covered the production of bio-n-butanol from corn at Green Biologics’ production facility in Minnesota, USA. *
The methodology used in this report considers carbon contained in petrochemical butanol as fossil derived and the carbon produced during GBL’s production process as biogenic. Based on these assumptions, we can achieve GHG savings for bio-butanol of ~44% against its petrochemical counterpart.
As methods vary between standards, the data is summarized in four different ways to account for the effect of varying allocation method impacts on results.
The graph below shows the GHG emissions of Green Biologics butanol and the savings achieved when compared to its petrochemical equivalent.
The report focuses on the carbon footprint of bio-butanol, so a detailed GHG analysis was not conducted on acetone. The process for acetone is identical to butanol up until distillation where the products are separated and further purified. n-butanol purification is more energy intensive than acetone, however since the system is integrated a safe assumption would be to use the same carbon footprint for butanol and acetone, cradle-to-gate.
- GHG emissions of construction, maintenance and machinery.
- Carbon sequestered in the soil from ploughing under crop residues (corn stover).
- Nitrous oxide emissions associated with the ploughed under residues.
- Global Warming Potential (GWP) is based on 2007 IPCC Fourth Assessment Report.
- Information on corn cultivation is based on US farming practice average data.
- Transport assumes all corn is sourced from a 100km radius, which matches our current harvest area.
- Carbon dioxide released from the fermentation process is not currently captured or sold.
- Co-products of DDGS (Distillers dried grains with solubles) and stillage are assumed to be dried for commercial sale.
- Currently, all co-products: DDGS and stillage are sold wet, not dried.
The next steps
This study was completed in 2016, based on early stage data before construction of the plant was complete and prior to start-up. As we continue to improve performance and work on improving the process required for drying of DDGS for animal feed, we expect to achieve further GHG savings and as such plan to update this analysis based on current data. The revised analysis will also take into account the practice of ‘no-till’ farming, a method carried out in Minnesota where the solids are not ploughed between seasons. This system eliminates nitrous oxide emissions and has other net GHG benefits.
The updated study will follow the approach laid out in the Life Cycle Metrics for Chemical Products guidance, which was developed by the World Business Council for Sustainable Development (WBCSD) to align life cycle metrics of chemical product life cycle assessments. This method builds on the ISO standards and the International Reference Life Cycle Data System (ILCD) guidance by providing additional guidance specific to the chemical sector.
* This analysis is by Green Biologics.