Offensive waste valorisation in the UK: Assessment of the potentials for absorbent hygiene product (AHP) recycling

Offensive human waste refers to non-hazardous waste that contains body fluids from non-infectious humans, comprised of post-consumer Absorbent Hygiene Products (AHPs), swabs, dressings, bedding, gloves, and other materials. While this waste category requires more stringent handling, storage and disposal measures than general waste, its non-hazardous nature suggests that there are opportunities for waste valorisation. An inventory of 200 offensive human waste bags collected from various healthcare institutions in South-Eastern England show that about 76% of the waste is comprised of AHPs, most of which are adult incontinence pads and child nappies. Mixed plastics comprised of predominantly HDPE represent 9% of the waste. To evaluate the potentials for offensive human waste valorisation, small-scale separation tests involving artificially-soiled nappies and associated mixed plastic packaging wastes have been performed. Findings suggest that about 50% of the total superabsorbent polymer is recoverable from fluff pulp fractions, recoveries of which are unaffected by the presence of ionic species typically present in human waste. On the other hand, recovery of mixed plastic packaging is more challenging. Overall, however, findings suggest that viable AHP recycling is possible if recyclate materials are targeted towards non-food related markets outlets such as the construction and land remediation sectors.

Phosphate and ammonium sorption capacity of biochar and hydrochar from different wastes

The potential for biochar and hydrochar to adsorb phosphate and ammonium is important for understanding the influence of these materials when added to soils, compost or other high nutrient containing environments. The influence of physicochemical properties such as mineral content, surface functionality, pH and cation exchange capacity has been investigated for a range of biochars and hydrochars produced from waste-derived biomass feedstocks. Hydrochars produced from hydrothermal carbonisation at 250 °C have been compared to low and high temperature pyrolysis chars produced at 400-450 °C and 600-650 °C respectively for oak wood, presscake from anaerobic digestate (AD), treated municipal waste and greenhouse waste. In spite of differences in char physicochemical properties and processing conditions, PO4-P and NH4-N sorption capacities ranged from about 0 to 30 mg g(-1) and 105.8-146.4 mg g(-1) respectively. Chars with high surface areas did not possess better ammonium adsorption capacities than low surface area chars, which suggests that surface area is not the most important factor influencing char ammonium adsorption capacity, while char calcium and magnesium contents may influence phosphate adsorption. Desorption experiments only released a small fraction of adsorbed ammonium or phosphate (<5 mg g(-1) and a maximum of 8.5 mg g(-1) respectively).