Grundfos – Team 2.IN – Next Generation Water Action

Lignin based Bio-absorbent Capsule: A green and sustainable solution to increase soil moisture retention potential and crop yield

Waste to Value

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

Challenges

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.

Expensive irrigation technologies

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).

Proposed solution

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.

Highlighting the product‘s advantages

How would it benefit agriculture and hence the farmers?

The bioabsorbent capsules are highly economical, as it is developed from paper-pulp industry waste, lignin, that has low commercial value, therefore easily accessible to all farmers. The estimated cost is $ 2-3 per kilogram of capsules, highly economical compared to cellulose-based gels and synthetic chemical-based hydrogels which cost around $14-19/kilogram and $ 5-10/ kilogram, respectively.
The hydrophilic capsules serve as super soakers, will result in high crop yield with the limited frequency of irrigation (i.e., 20-50% reduction in irrigation frequency). It would promote sprouting and seedling development by providing optimum moisture for quick germination resulting in better farm success.
The super absorbent capsules have the capability to trap irrigation and rainwater and act as local micro-water reservoirs at plant roots that can be stored and gradually released over prolonged durations. It can reduce plant stress, which usually occurs due to moisture scarcity, by gradually dispensing moisture to the root zone.
It can considerably reduce the application of synthetic fertilizers such as NPK fertilizer as the chemicals so adsorbed with water will slowly release, hence, extend the operational life and uptake efficiency by root systems.
The amount of absorbent required will depend on the soil characteristics such as for arid and semi-arid regions, 1-1.5kg per acre is estimated, which is quite less than the commercially available polymer gels, that utilizes 6-10 kg/acre.

Product roadmap

Business Plan

Future Plan

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.

Conclusion

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.

Our Team

References