Alternative Materials for the Enrichment of Biogas with Methane

Abstract

Carbonaceous adsorbents have been pointed out as promising adsorbents for the recovery of methane from its mixture with carbon dioxide, including biogas. This is because of the fact that CO2 is more strongly adsorbed and also diffuses faster compared to methane in these materials. Therefore, the present study aimed to test alternative carbonaceous materials for the gas separation process with the purpose of enriching biogas in biomethane and to compare them with the commercial one. Among them was coconut shell activated carbon (AC) as the adsorbent derived from bio-waste, rubber tire pyrolysis char (RPC) as a by-product of waste utilization technology, and carbon molecular sieve (CMS) as the commercial material. The breakthrough experiments were conducted using two mixtures, a methane-rich mixture (consisting of 75% CH4 and 25% CO2) and a carbon dioxide-rich mixture (containing 25% CH4 and 75% CO2). This investigation showed that the AC sample would be a better candidate material for the CH4/CO2 separation using a fixed-bed adsorption column than the commercial CMS sample. It is worth mentioning that due to its poorly developed micropore structure, the RPC sample exhibited limited adsorption capacity for both compounds, particularly for CO2. However, it was observed that for the methane-rich mixture, it was possible to obtain an instantaneous concentration of around 93% CH4. This indicates that there is still much potential for the use of the RPC, but this raw material needs further treatment. The Yoon–Nelson model was used to predict breakthrough curves for the experimental data. The results show that the data for the AC were best fitted with this model.

Possibilities of Biogas Upgrading on a Bio-Waste Sorbent Derived from Anaerobic Sewage Sludge

“…The higher inflow rates of 10 L/min and 15 L/min ensured the methane content in upgraded biogas at the level of 87.4% and 84.3%, respectively. Bałys et al [55] conducted breakthrough experiments using sorbents derived from bio-waste materials for biogas upgrading. They found that coconut shell activated carbon as the sorbent ensured the purity of biogas initially containing 25 v% CH 4 and 75 v% CO 2 on the level of above 95 v% CH 4 .…”

Effect of Walnut-Shell Additive on the Structure and Characteristics of Concrete

“…The study presented in this article develops the ideas of the concept of sustainable environmentally friendly concrete, which implies the partial and complete replacement of the mineral components of concrete with natural and rapidly renewable analogues. Replacing large-mineral aggregate with walnut shells will partially eliminate complex mechanized and energy-intensive production processes associated with high greenhouse-gas emissions [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. At the same time, it is important to find a balance between the strength and density of the resulting composite, so that a decrease in the SC of the material is accompanied by a commensurate decrease in the density of the material.…”