Farms, cities, and industries generate enormous volumes of organic waste every year, and much of it goes to landfills or is burned rather than put to productive use. A new review, published ahead of print in Current Agricultural Sciences, makes the case that this waste could instead become a resource for healthier soil and more resilient farming — if two waste-derived soil treatments, microbial biofertilizers and biochar, are used together rather than separately.
The study, conducted by Biplab Debnath and Shaileyee Das and published in Current Agricultural Sciences, argues that combining microbial biofertilizers with biochar — both made from waste — offers more benefit to soil and crops than either treatment alone.
Biofertilizers and biochar are both already established, individually, as ways to improve soil without relying purely on synthetic chemical fertilizers. Biofertilizers are living microbial inoculants — beneficial bacteria or fungi added to soil or seeds — while biochar is a stable, carbon-rich material produced by heating organic matter, such as crop residues, in a low-oxygen process.
The review highlights that both can be produced from the same underlying raw material: agricultural, municipal, and industrial organic waste streams. Despite that shared starting point, the authors note that research on producing and applying these two treatments together, rather than as separate products, remains a comparatively underexplored area.
What each treatment contributes
According to the review, waste-derived microbial biofertilizers support plant growth through several mechanisms: helping fix atmospheric nitrogen into a form plants can use, increasing the availability of soil phosphorus, supplying micronutrients via specialized microbial compounds called siderophores, producing plant growth hormones, and suppressing disease-causing soil organisms. The review also notes that liquid formulations of these biofertilizers tend to maintain microbial populations more stably and actively than other formats.
Biochar contributes in a different, complementary way. Since it is produced through a heating process, it forms a carbon structure that resists breakdown, allowing it to store carbon in the soil over the long term. Beyond carbon storage, the review describes how biochar improves the physical and chemical properties of soil, increases its capacity to hold onto and supply nutrients (measured as cation exchange capacity), and creates a protective physical structure where beneficial soil microbes can shelter and thrive.
More than the sum of their parts
The central argument of the review is that applying biofertilizers and biochar together consistently outperforms using either one on its own. Across the evidence reviewed, co-application was associated with better nutrient-use efficiency, higher soil enzymatic activity, greater plant biomass, and improved plant resilience to both environmental stress, such as drought, and biological stress, such as disease or pests. In practical terms, biochar appears to provide beneficial microbes with a more stable home in the soil, while the microbes actively cycle nutrients that plants can use, and the two effects reinforce each other.
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Despite this promise, the review highlights the hurdles to broader adoption. These include inconsistent performance when treatments move from controlled trials into real-world fields, limited survival of beneficial microbes over time, variability in product quality between batches or producers, cost barriers for farmers, and a lack of adequate extension services to help farmers learn how to use these products effectively.
The way forward
Looking forward, the review points to several developments that could help close these gaps: using “omics” technologies (large-scale genetic and molecular profiling) to identify and optimize the best-performing microbial strains, engineering microbial communities designed to work well together, chemically modifying or functionalizing biochar to enhance its properties, and developing clearer regulatory frameworks to support the quality and consistency of these products.
The authors suggest the combined use of biofertilizers and biochar, produced through waste valorization, as a scalable strategy within a broader circular bioeconomy — one that could improve soil health, reduce reliance on chemical fertilizers, and help agriculture adapt to a changing climate.
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