Sewage biogas efficient purification by means of lignocellulosic waste-based activated carbons

Abstract

The present paper evaluates the efficiency of sustainable activated carbons obtained from the valorization of lignocellulosic waste in removing siloxanes and volatile organic compounds for the purification of anaerobic digester biogas. Pyrolized and non-pyrolized lignocellulosic residues generated in food and wood industries were used as precursor materials to obtain experimental adsorbents by a chemical activation process using several activating agents. The highest porosity was obtained by non-pyrolized residue activated by K 2 CO 3 at 900 ºC. The performance of the experimental materials was compared with that of commercial activated carbons in gas adsorption tests of siloxanes (octamethylcyclotetrasiloxane and hexamethyldisiloxane) and volatile organic compounds (toluene and limonene). The waste-based activated carbons developed in this work proved to be more efficient for the removal of both siloxanes and VOCs than the commercial samples in most of the conditions tested. Adsorption capacities correlated with porosity, while the more relevant pore size depends on the adsorbate.

More Sustainable Chemical Activation Strategies for the Production of Porous Carbons

“…400 °C), [36,39] which explains the lower pore development achieved with K 2 CO 3 compared to KOH (Table 1). [40–44] Besides, as mentioned above, K 2 CO 3 is one of the products during KOH activation, so that for T >600–700 °C, reactions (1) to (4) also take place during KOH activation, yielding additional pore development. However, K 2 CO 3 has two important additional advantages over KOH.…”

Technical Challenges and Optimization of Biogas Plants

“…However, previous experiences of difficulties in reactor handling, lack of policy framework and technical support in this field are a major bottleneck identified in this paper. It is suggested that biogas plant designers/engineers should always be mindful of leakages, solid retention time, and pressure management for sustainable [92,93] Hydrogen recovery Extracting H 2 gas as energy source [94] Pressure transducer Methane pressure monitoring [95] pH Self-regulation ternary buffer system Process stability [96] VFA control Process stability [97] ORP monitoring and control system…”

Environmental Decision Support System for Biogas Upgrading to Feasible Fuel

“…Adsorption onto activated carbon is one of the technologies with the highest overall removal efficiency, although it has a limited efficiency for small siloxane molecules, such as hexamethyldisiloxane [49]. However, the frequently required replacement of the exhausted adsorbent beds [24] increase the operational costs associated, obtaining a score of just 5 in OPEX criterion. Inorganic adsorbents [45,50] are not only more expensive than activated carbon, but also the lifespan of the adsorbent bed is shorter, which considerably increases the OPEX (2.5 points).…”

“…Physical absorption, currently commercial for siloxane elimination, accomplishes moderate elimination efficiencies and is usually combined with other treatments such as refrigeration [22]. Non regenerative adsorption onto AC is the most widely used to reduce siloxane concentration [23], since it is low energy-consuming and highly effective [24]. Biotrickling filters and membrane separation systems are emerging techniques, although currently under research [25].…”