Brown County Organics adopts Dürr’s Sorpt.X SB technology for pure biogas production

Dürr's Sorpt.X biogas purification system was recently installed at Brown County (BC) Organics, a grant-funded anaerobic digester facility owned by Dynamic Renewables.
The facility, which held a ribbon cutting ceremony on 10 November, is located in Greenleaf, Wisconsin, and is the first commercial biorefinery of its kind in the United States. It will utilise 16 digesters to produce renewable natural gas (RNG), fibre bedding and clean water. Start-up will take place in early 2023.
Dürr designed, manufactured and commissioned the Sorpt.X SB system installed at BC Organics. It has a capacity of 2,400 square cubic feet per minute (SCFM) with hydrogen sulphide (H2S) removal and post compression. The system will produce about 1,630 million British thermal units (MMBtu) of renewable natural gas each day.
"The system takes the 60% methane, 40% carbon dioxide (CO2) gas mixture produced by anaerobic digestion of manure and upgrades it to 98% pure methane for injection into the Guardian pipeline, which is a small natural gas pipeline that brings gas from northern Illinois into Wisconsin," said Tim Golden, director of alternative fuels at Dürr's Clean Technology Systems division. "There it will be used to create compressed natural gas for vehicles, replacing more than 11,000 gallons of diesel fuel each day and decreasing dependency on fossil fuels."
Eleven local dairy and beef farms will provide more than 900,000 gallons of manure to the anaerobic digester facility each day using a hub and spoke system. In addition to creating renewable natural gas, the project aims to protect natural resources by reducing potential greenhouse gas emissions and decreasing the amount of manure applied to the land.
After the manure has been digested, the solids will be dried and separated to create more than 135 tons of fibre bedding for cows each day. The remainder will be sold to the horticultural market for use in boxing mixes and as a replacement for peat moss. This process will significantly reduce the amount of phosphorus released into the Lower Fox River watershed in Wisconsin as well.
BC Organics will also produce more than 400,000 gallons of clean, dischargeable water per day using ultrafiltration and a forward/reverse osmosis system. Each participating farm will receive clean water in exchange for its manure, resulting in a reduced need for local ground water. As an added benefit to the local communities, the anaerobic digestion process will also reduce odour by more than 90%.
"BC Organics is providing a more sustainable manure management option for the farms it will serve," said Golden. "When coupled with the ability to make renewable energy and recycle resources, it's a clear win for the community and environment."