Commissioned in October 2020, the Raízen biogas power plant in Guariba, Brazil now generates energy using agricultural by-products. The Penetron System – including PENETRON ARC, an innovative acid-activated coating specifically designed for anaerobic and biogas conditions – was specified to ensure a waterproof and durable solution for the plant’s concrete structures.

The $28 million project, located in Guariba, in the state of S?o Paulo, generates 21 MW of installed capacity, making it one of the largest biogas power plants in the world. Raízen, the plant owner and operator, utilizes vinasse (slop leftover from distillation) and filter cake (residue from sugar cane juice purification), both by-products from sugar cane processing by an adjacent sugar cane plant. This plant crushes over 5 million tons of sugar cane annually, furnishing an endlessly renewable energy source for the Raízen biogas power plant.

Biogas energy generation is the result of a complex process. It begins with biodigesters converting organic matter, such as the vinasse and filter cake, into methane and CO₂ (i.e., biogas). This biogas is then transformed into clean, electric energy by motor generators.

“The Raízen project represents a revolution in the use of agro-industrial waste,” explains Cláudio Neves Ourives, Managing Director of Penetron Brazil. “And it shows the potential of agricultural waste as a source of clean, renewable energy.”
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Concrete Waterproofing & Acid Resistance

During the planning stages of the Raízen biogas plant project, the engineers at Lelis & Arruda Engineering and PROMON, the general contractor, asked Penetron Brazil to help develop a solution to protect the plant’s concrete structures from both the region’s high water table and the aggressive chemical environment of the biogas tank.

PENETRON ADMIX, a crystalline waterproofing admixture, was used to treat 4,000 m³ (5,000 yds³) of concrete for all the tanks, including the critical biogas tank. PENEBAR SW-55 swellable waterstop strips were used to seal the construction joints. PENETRON, a topical crystalline material, and PENECRETE MORTAR, were used to seal the tie-holes. PENETRON ARC, an innovative active mineral protective coating specifically formulated for anaerobic (and biogas) conditions, was topically applied to the gas zone of the biogas tank to protect the concrete from attack from sulfuric acid (H₂SO₄), a by-product of the biogas generation process.
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Increasing Resistance to Acid Attack

The concrete in the Raízen plants biogas tank is regularly exposed to biogenic sulfuric acid attack, which can quickly deteriorate the concrete matrix and the embedded reinforcing steel – shortening the lifespan of the tank. The protective PENETRON ARC coating is activated when exposed to the aggressive acids, especially the sulfuric acid found in the Raízen biogas plant.

“When PENETRON ARC reacts to the acids in the biogas tank, it is transformed into a dense, acid-resistant shell, which actually helps create a denser, more impenetrable matrix. In fact, strong acidic environments increase the acid resistance abilities of PENETRON ARC,” explains Cláudio Neves Ourives. “This coating protects and prolongs the life of the concrete substrate, even in the harsh conditions of the Raízen biogas tank.”