Brazil is the world’s leading producer and exporter of sugarcane, accounting for approximately 50% of global sugar production. Annually, the country produces around 654.8 million tonnes of sugarcane, 41.25 million tonnes of processed sugar, and 29.7 billion litres of ethanol. The substantial production volume positions Brazil as a global pioneer in biomass energy, particularly through sugarcane bagasse utilization. Hundreds of power plants across the country utilize sugarcane bagasse as fuel—mostly through direct combustion—many operating with capacities well over 1 MW.
In recent years, leading companies in the sector have shown growing interest in biogas generation, which not only enhances the energy output of sugarcane-based biomass systems but also holds significant potential to reduce the carbon footprint of cane production.
CG (a pseudonym used in compliance with client confidentiality requirements), one of Brazil’s largest sugar and ethanol producers, recognized the opportunity for biogas implementation. In October 2021, CG established its first biogas plant in Narandiba (São Paulo state) in partnership with GBT(a pseudonym used in compliance with client confidentiality requirements), a company specializing in biogas generation solutions. With GBT’s technical support, the biogas plant utilizes multiple feedstocks: vinasse-a by-product of ethanol production-during regular operations, sugarcane bagasse during harvest season, and filter cake during off-season periods. This multi-feedstock approach effectively mitigates the seasonal limitations typical of biogas production and enables continuous operation year-round.
Measurement Requirements
Hydrogen sulfide (H₂S) is a common and problematic impurity in biogas. It can inhibit methane (CH₄) production and cause severe corrosion in equipment. Therefore, accurate and reliable measurement of H₂S is crucial in biogas monitoring.
Due to the high protein content in vinasse, the H₂S concentration in biogas from ethanol production can reach up to 1.5%, which is significantly higher than that from other feedstocks. Traditional ECD (electrochemical detector) H₂S sensors tend to have a short lifespan under such conditions, resulting in frequent and costly replacements.
To reduce maintenance demands and enhance monitoring reliability, a gas analyzer equipped with a long-lifespan H₂S sensor was required for effective biogas system operation.
Solutions
After evaluating various technologies and suppliers, CG selected the Gasboard-3500UV gas analysis system from Cubic Instruments, which is based on UV-DOAS (Ultraviolet Differential Optical Absorption Spectroscopy), NDIR, and ECD technologies.
Gasboard-3500UV analyzer features a long-lifespan H₂S sensor and supports three independent sampling channels, enabling continuous, real-time monitoring of multiple digesters with high accuracy and low maintenance requirements.
System Components
- Sampling Unit: Housed in an explosion-proof enclosure, the integrated sampling unit includes a sampling pump, a three-channel control board, solenoid valves, and control software. The sampling unit extracts low-pressure, unstable gas samples from three different digesters simultaneously.
- Pretreatment Unit: The pretreatment system includes a gravity-based dewatering tank, gas-water separator filter, flow regulator, and vortex cooler. These components effectively remove dust, moisture, and other impurities, ensuring a clean and stable gas flow to the analyzer.
- Analysis Unit: The Gasboard-3500UV analyzer combines multiple detection technologies (UV-DOAS, NDIR, and ECD) in an explosion-proof design. It enables high-precision, continuous monitoring of H₂S, CO₂, CH₄, and O₂ concentrations in real time—without requiring an external air purge.
Value to Customer
By implementing the UV-DOAS, NDIR, and ECD based Gasboard-3500UV system, CG can continuously monitor the anaerobic fermentation process in real time, allowing timely adjustments to optimize digestion performance. This improves the stability and efficiency of biogas and biomethane production.
The stable and reliable biomethane output enabled CG to successfully secure a contract for supplying biogas to three nearby cities, Narandiba, Pirapozinho, and Presidente Prudente, with a combined population of 264,000 residents.
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