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Anaerobic digestion (AD) is an important technology to produce biogas from dairy manure. Although the AD of dairy manure results in the harnessing of the energy contained in manure, most of the nutrients (phosphorous and nitrogen) remain in the liquid effluent, representing an important source of pollution. Additionally, the biogas produced contains H2S and CO2, limiting its practical use as fuel. In this paper, we report the production and use of a carbonaceous adsorbent from AD fibers for the removal of hydrogen sulfide (H2S) from biogas and phosphate (PO4 3−) from aqueous liquid effluents. The adsorbents studied were produced via slow pyrolysis between 350 and 800 °C followed by CO2 activation. The elemental and proximate analyses, surface area and pore size distribution of each of the adsorbents studied are reported. Their adsorption capacities were assessed using H2S breakthrough and PO4 3− batch equilibrium tests. The sorption capacity varied between 21.9 and 51.2 mg g−1 for H2S and between 4.9 mg g−1 and 37.4 mg g−1 for PO4 3−. Commercially available activated carbon studied adsorbed 23.1 mg g−1 H2S and 15.7 mg g−1 PO4 3−. The results show that the retention of H2S and PO4 3− compounds were governed by the ash content, surface area and pH. Adsorption mechanisms for H2S and PO4 3− sorption are proposed. © 2018

Dairy farmers worldwide are facing the difficulty of managing or disposing of dairy manure. Anaerobic digestion (AD) is an option for treating dairy manure and producing biogas. A byproduct of AD is fiber, which is only partially being used despite its potential for different products, including wood plastic composites (WPCs). However, some properties of WPCs need to be improved to use them in high moisture content environments. This work evaluates the effect of hot water extraction (HWE) (at 160 °C for 60 min) of the AD dairy fiber on properties of WPCs. WPCs were produced using AD fiber via extrusion and tested for mechanical properties and water affinity. The WPCs produced with HWE fiber exhibited increased mechanical strength (36%) and stiffness (30%), and reduced strain at break (15%) compared to composites produced with untreated fiber. Water sorption and thickness swelling were reduced by 39% and 36%, respectively, after immersion in water for 98 days. The diffusion constant of WPCs produced with HWE fiber was also reduced by 64%. These results show that HWE is an effective method for enhancing mechanical properties and reducing hydrophilicity of WPCs produced from AD fiber.