(612g) Exploring Lignin Based Biorefinery in India

A.K.Ray and N.C.Mishra

Department of Paper Technology, Indian Institute of TechnologyRoorkee

Saharanpur Campus, Saharanpur-247001, UP , India

ABSTRACT

Lignin is one of the versatile chemicals , nature has ever produced. These biomaterials are abundantly available in plant biomass and can be utilized as such or as derivatives for various  applications. It can be utilized as dispersants for a variety of iorganic materials ,e.g., clay, cement, calcium carbonate, and titanium dioxide, asphalt emulsifiers and emulsion stabilizers, base for industrial detergents(washing powders and liquid soaps),drilling mud thinner, surfactants, coagulants and flocculants(for sewage and waste water treatment), retention aids, fire retarding agents( chlorobrominated lignin),drug formulation, catalyst substrate, carriers for adhesives, insecticides and herbicides, as plastics,binders and adhesives such as lignin reinforced polymers, and graft polymers including polyurethanes, polyesters, polyamines and epoxies, and rubber additives. The main lignin polymers are lignin sulphonates which  are used in emulsification, defloccuation, chelation, adsorption and adhesion. The most important applications are for oil well drilling muds, cement and concrete additives, protein precipitants ,sequestering agents, dispersants for a variety of products such as refractories, tiles, absorbants, cosmetics, crayons, medicines, paint, paper coatings, tooth powder and dyes, ore floatation, and electrolytic refining,tanning agents , ion-exchange resins etc. Other uses of lignosulphonates are lime plastering medium, storage battery plates-as expander and component of separator., lime plaster-use of less water with improved settling properties, crystal growth inhibitor, Ingot mold wash, and many more. Lignin- polyisocyanate/polyurethane foam,lignin-urea/phenol formaldehyde, thermosetting resins, lignin-starch, lignin-geletin,glues with polyvinyl alcohol/ acetate, are some of the notable examples as biodegradable polymers and composites. Some low molecular weight compounds like vanillin, dimethyl  sulphonates, dimethyl sulphoxide, furfural, methyl mercaptan, phenolics can also be obtained from lignin.

The main source of lignin and its derivatives in pulp and paper industry  is  black liquor or soda liquor and sulphite waste liquor though lignin can also be obtained from liquor obtained from steam explosion, hydrothermolysis  and pure organosolv process.

Presently Indian pulp and paper industry is passing through a crisis from various angles including scarcity of raw materials  and has been rated as highly capital , energy  and pollution intensive. Majority of mills using non-forest-based raw materials and agricultural residues( rice straw, bagasse, wheat straw etc.) discharge these valuable chemicals to waste on one hand and polluting the environment to a large extent on the other. These chemicals are also non-biodegradable. According to rough estimate for every ton of bleached pulp produced, about 0.5 ton of lignin is either wasted to sewer or used as a low value fuel. Though some Indian  industries of the later category have attempted to  design recovery plant or bio-methanation process  or to recover lignin based chemicals, it is not very wide spread practice. The process of lignin isolation and separation though known from many years, has not been practiced in industrial scale. The major problems lie in the process of  isolation of lignin or its substitutes from sulphite liquor as lignin sulphonates or from  kraft process ,the thiolignin, and soda lignin from soda liquor by chemical modification.

The profitable utilization of lignin can be possible by various chemical modification process. These include alkylation or arylation( to produce ethers), carboxylation( to form esters), polymeric condensation products with phenols, aldehydes  and amines, phenol derivatives with salt of heavy metals, nitration, halogenation( chlorination,chloro-bromination) or oxidation, oxyalkylation,de-methylation,sulphonation or sulpho-methylation to produce lignin sulphonates and many other unit processes.Some of the processes are  established in  industry but the majority of these are yet to be  develop in commercial scale. With the continual  increase in price of crude petroleum , there might be a large price margin existing between low cost abundantly available lignin and some high cost petroleum products. The incentive to develop cost effective   lignin technology to produce marketable lignin based products replacing the petrochemicals  needs to be explored urgently.

 In this present paper various alternative schemes for precipitation of lignin, removal by filtration at optimum conditions of temperature and pressure,  followed by purification and re-precipitation and finally conversion to value added products are analysed from the view point of commercial applications. These lignin based bio-products are mostly imported. It has been found that some products are quite competitive with other commercial products. But industry is still hesitant to invest funds to  manufacture these chemicals from lignin because of fear of high risk. If  it is possible to separate lignin economically from spent pulping liquor and to convert it to usable chemicals, the financial returns might be sufficient to support this industry. This is an imperative  necessity now for  sustainability of nonwood agri-residue based mills in India. In this present investigation a brief account on the lignin utilization in Indian context is reported and a feasibility study on the  techno-economics is presented.