Lignin based Bio-absorbent Capsule: A green and sustainable solution to increase soil moisture retention potential and crop yield
Value addition of paper-pulp industry waste, lignin into bio-absorbent capsules as a green & economical hydrogel technology for agriculture particularly in water-scarce zones as a micro-reservoir for retaining soil moisture for prolonged duration and as agrochemical carrier.
Waste valorisation for agricultural water conservation
Water Scarcity & Agriculture
Worldwide about 42% of the land is affected by drought, in India, it’s more than 50%, of which 6% is exceptionally dry (1). The rising population is directly proportional to the demand for crop production, which necessitates a massive amount of water. Apart from India, other semi-arid regions of Asia, the Middle-East and Sub-Saharan have witnessed a steady decline in irrigation water potential(2). Despite electricity subsidies, farmers are unable to bear pumping costs due to dropping groundwater levels.
It is worth noting that in India small and marginal farmers contribute about 98 million of the total 120 million farm holdings; hence, net earnings from small farms makes farmers hesitant to adopt water management practices such as drip irrigation and use of sprinklers in agriculture(3),(4).
Direct application of water requires an ample amount of water supply to crops from the surface, which results in only 50% utlization of water, while the remaining is lost as runoff and by evaporation.
However hydrogel technology helped the farmers to enhance the cultivation of plants with low irrigation cost. But the hydrogels based on polyacrylates/ polyacrylamides are too expensive compared to the conventional soil amendments per square feet, hence less accessible to small-scale farmers. It is persistent; once you have applied you can’t get rid of it. These petrochemical-based gels Iasts for more than five years.
Paper-mill waste accumulation
The majority of the paper-pulp industry, particularly small paper mills are generating millions of tons of lignin as a waste every year which is either being discarded or burned as a low-cost fuel. These industries based on wood and agro-biomass residue are pulping fibrous raw material by utilizing drastic alkaline conditions to separate fibre from lignin. In hot alkaline conditions, lignin dissolves and separates as lignin-rich black liquor (5).
Our aim is to create an environmentally friendly and sustainable irrigation solution by developing lignin-based bioabsorbent capsules that will help in mitigating the world’s water scarcity problems while also increasing crop production with minimal chemical pesticide use.
Plant biomass undergo various pretreatment process in paper industry that result in cleavage of cellulose, hemicellulose from lignin. The industry consume cellulose and hemicellulose for paper manufacturing and the rest lignin is mostly burned as low cost fuel or just discarded. Here we utilized the waste lignin in combination with synthetic/natural polymer for bioabsorbent capsules development.
The bioabsorbent capsules are rich in phenolics, carboxylates and hydroxyls and hence responsible for the water absorption mechanism. This lignin bioabsorbent (the sample product image on the side) acts as super soakers and absorbs water up to 350-500 times the capsule weight and can freely release 95% water of the same under suction pressure by plant roots. This would overcome the three most common soil conditions that obstruct plant growth and yield, that is, low water retention capacity, high evapotranspiration rate, and leaching of soil moisture. The capsules would directly promote soil permeability, texture, structure, evaporation and infiltration rates of water. Soil erosion caused by stormwater run-offs can be greatly reduced, particularly in sloped terrains. Apart from these, the capsules also protect plant and soil from damage caused by conditions such as unanticipated drought conditions, soil erosion and salination, and the overuse of chemical fertilizers and pesticides, which often cause irreversible damage to soil biota as well.
How would it benefit agriculture and hence the farmers?
In addition to achieving our target goal, we will explore the bio-absorbent applications in other sectors such as industrial effluent treatment.
Since lignin is abundant in polyphenolic structures, hence finds many applications besides water-absorbing agents such as a natural sequestering agent for micropollutants including pharmaceuticals, detergents, industrial chemicals, pesticides, and many other contaminants.
Short Term Goal
Lignin-based hydrogel granules- Hydrogel formation via polymerization reaction pathway. The hydrogel utilizes lignin without further modification that has been extracted directly from black liquor generated in the paper-pulp industry. The developed hydrogels can be used as an adsorbent for the removal of pollutants such as dyes, toxic metal ions, and other pollutants present in industrial effluent.
Long Term Goal
Modified-Lignin-based Adsorbent- Chemical modification of lignin for the introduction of functional groups such as amides, carboxyls, sulfonyl, etc. The structural modification would enhance thermal stability and mechanical strength and improve adsorbing efficiency. The hydrogel can be molded into membrane form for effective removal of pollutants.
Our purpose is to develop and deliver eco-friendly, sustainable and cost-effective hydrogel technology as an alternative to petrochemical-based gels for irrigation. Similar to synthetic hydrogels, lignin-based bio-absorbents can minimise irrigation frequency, saving water and labour costs while also help face drought condition. However, unlike synthetic hydrogels, it is made from plant waste, making it a renewable and environmentally friendly option. It enables farmers to produce higher-yielding crops with less fertilizer and pesticide use, thereby improving soil quality and preventing soil compaction.