Renewable Natural Gas (RNG) and Biochar Production from Sugar Beet Residues

Commodities

Practices

Sugar beet processing at Wyoming Sugar Company produces more than 100,000 tons annually of pulp and desugared molasses. Much of this material is currently handled as low value feed, compost, or landfill. The uncontrolled decomposition releases odors, which cause environmental concerns and overlook an important economic opportunity. This project seeks to integrate anaerobic digestion (AD) and pyrolysis systems that can convert these residues into renewable natural gas (RNG) and digestate-derived biochar to improve soil and wastewater management, and increase producer revenue in Wyoming. The research will characterize beet pulp and molasses streams from Wyoming Sugar, conduct lab scale AD tests to measure biogas and RNG potential as well as digestate quality, and pyrolyze digestate to produce and analyze biochar for potential soil amendment and odor control uses. This sequential processing pathway couples energy recovery from soluble organics with biochar production from digestate, closing waste and energy loops in agriculture.

Education and outreach will include two structured producer consultations and annual visits with Wyoming Sugar growers and UW Extension personnel. These visits will involve roundtable discussions, producer focused reviews, and educational meetings to interpret results together, identify adoption barriers, and support decision making on the integration process.

Expected outcomes include quantified RNG and biochar yields, literature-based evaluation on soil amendment and odor control potentials. As well, producer awareness will increase on waste valorization alternatives and sustainable ways to improve environmental performance, diversify revenues, and build long term resilience for sugar beet producers in Wyoming.

Research Objectives

Sugar beet processing at Wyoming Sugar Company generates large amounts of residual beet pulp and desugared molasses that are under‑utilized, and by-product streams contribute to odor issues from storage ponds that affect nearby residents. Anaerobic digestion (AD) of sugar beet pulp and molasses can result in high biogas yields that can be upgraded to Renewable Natural Gas (RNG) for pipeline injection or on‑site energy, as sugar production is an energy intensive operation and rising costs of energy is a concern to manufacturers. Digestate generated by AD remains nutrient‑rich and could be transformed into biochar via pyrolysis, offering a suitable soil amendment and odor‑control sorbent [17].

The focus of this project is to evaluate an integrated pathway to the transformation of sugar beet residues, including pulp and molasses, into RNG and biochar, thereby increasing producer revenue while producing materials to increase soil health and moisture holding capacity, as well as reduce the odor produced by the discharge of sugar-beet processing wastewater into ponds. We will target the following specific, measurable, attainable, realistic, and time‑bound objectives in this project.

Research Objective 1 (Year 1): Characterize sugar beet pulp and molasses streams and develop lab‑scale anaerobic digestion experiments to evaluate biogas/RNG potential and digestate amount and composition under conditions pertinent to Wyoming Sugar Company.

Research Objective 2 (Year 1): Conduct a literature-based analysis of digestate-derived biochar potential to (a) improve water retention and fertility in Wyoming-relevant agricultural soils and (b) adsorb odor-causing compounds, such as those expected from wastewater ponds.

Research Objective 3 (Year 2): Convert the digestate solids to biochar via controlled pyrolysis and then characterize the biochar properties to estimate its effectiveness for use in soil amendment and odor remediation.

Research Objective 4 (Year 2): Conceptualize a mass- and energy‑balanced commercial-scale AD and pyrolysis process for Wyoming Sugar Company based on experimental data.

Educational Objectives

Education and outreach play a central role in this project by translating technical findings on renewable natural gas and biochar production into practical knowledge aimed at producers. This approach supports informed decision-making, improves resource efficiency, and promotes long-term agricultural sustainability in Wyoming. To achieve this goal, the project sets specific, measurable, and time-bound educational objectives that organize stakeholder engagement and dissemination efforts throughout the project.

Educational Objective 1 (Year 2): Raise awareness among sugar beet producers and University of Wyoming Extension professionals of this project's research objectives, as well as increase UW researchers' understanding of producer challenges and constraints.

Educational Objective 2 (Year 3): Disseminate research findings and increase awareness among sugar beet producers and University of Wyoming Extension professionals of potential benefits from integrated anaerobic digestion and biochar systems for sugar beet residues.