Phosphorus, a vital nutrient for plants and ecosystems, often ends up in wastewater from agricultural and industrial activities. Excess phosphorus in water can cause eutrophication, harming aquatic ecosystems. To address this, researchers have developed a cost-effective solution: calcium/magnesium co-modified coffee grounds biochar (CMBC).

CMBC, created from spent coffee grounds, is an eco-friendly adsorbent with an impressive phosphorus removal capacity of 144.31 mg/g. It works by leveraging mechanisms like surface precipitation and electrostatic attraction, with calcium-based sites playing a dominant role. Once phosphorus is captured, CMBC-P (phosphorus-loaded biochar) can release 74.87% of the adsorbed phosphorus back into the soil over 60 days, enhancing soil fertility and promoting plant growth.

The study also highlights the environmental benefits of CMBC. Producing this biochar emits just 8.38 kg of CO₂ equivalents, significantly lower than other materials. A cost-benefit analysis reveals it as a highly economical solution, recovering 15.15 g of phosphorus per dollar spent.

By repurposing spent coffee grounds, this method not only addresses the waste issue but also provides a sustainable way to manage phosphorus pollution. It offers a dual benefit: removing excess phosphorus from water and recycling it as a fertilizer, contributing to agricultural sustainability.

This research underscores the potential of biochar as a low-cost, environmentally friendly tool for wastewater treatment and resource recovery, paving the way for broader applications in environmental and agricultural management.