Waste Utilization

Waste Utilization in Horticultural Crops
Dr.(Mrs.) Neelima Garg
Central Institute for Subtropical Horticulture, Lucknow
Email: [e-mail]

India has become one of the largest producer of fruits and vegetables in the world producing approximately 30 million tonnes of fruits and 60 million tonnes of vegetables annually. In recent years, there has been a shift from conventional farming of food grains to horticulture which include fruits, vegetables, ornamental crops, medicinal and aromatic plants, spices, plantation crops which include coconut, cashew nuts and cocoa and allied activities . With a huge population of 1.08 billion and population growth of about 1.6 % per annum, India is a large and growing market for food products. Its 350 million strong urban middle class with its changing food habits poses a huge market for agricultural products and processed food, which accounts for 32 per cent of the total food market. It accounts for US$ 29.4 billion, in a total estimated market of US$ 91.66 billion. The food processing industry is one of the largest industries in India. it is ranked fifth in terms of production, consumption, export and expected growth. According to the Confederation of Indian Industry (CII) the food-processing sector has the potential of attracting US$ 33 billion of investment in 10 years and generate employment of 9 million person-days. As a result there is a remarkable push in horticultural commodity processing sector .The installed capacity of fruits and vegetables processing industry has increased from 1.1 million tonnes in January 1993 to 2.1 million tonnes in 2006. The processing of fruits and vegetables is estimated to be around 2.2% of the total production in the country. The major processed items in the fruit and vegetable segment are fruit pulps and juices, fruit based ready-to-serve beverages, canned fruits and vegetables, jams, squashes, pickles, chutneys and dehydrated vegetables. Some recent products introduced in this segment include vegetable curries in retortable pouches, canned mushroom and mushroom products, dried fruits and vegetables and fruit juice concentrates. The fruits and vegetable processing industry is highly decentralized, and a large number of units are in the cottage, household and small-scale sector, having small capacities of up to 250 tonnes per annum. Since 2000, the food processing industry has seen significant growth in ready-to-serve beverages, fruit juices and pulps, dehydrated and frozen fruits and vegetable products, pickles, processed mushrooms and curried vegetables, and units engaged in these segments are export oriented.

However, processing of horticultural commodities generates two types of waste - a solid waste of peel/skin, seeds, stones etc -a liquid waste of juice and wash waters. In some fruits the discarded portion can be very high (e.g. mango 30-50%, banana 20%, pineapple 40-50% and orange 30-50%). These wastes are rich in organic constituents like, cellulose, starch pectin vitamins, minerals etc and posed serious health hazard problems due to high biological oxygen demand (BOD). Proper regulation of this waste is both a regulatory requirement as well as economic necessity. The composition of waste sugggest enormous potential for use as substrate for value added product.
One way of managing the situation is to reduce the loss and the other is to utilize the available material for the production of value added products. The utilization of waste will not only economizes the cost of finished products but also reduce the pollution level. The waste could be used for the production of fertilizers, fuel and other value added products through processing, extraction, hydrolysis or fermentation and as animal feed as detailed below:
Potential value products from fruits and vegetable waste
A number of beverages such as cider, beer, wine and brandy, and vinegar can be obtained from the fermentation of fruit wastes. Apple pomace has been utilized for the production of cider. Best quality of cider can be made by carbonating it. Good quality apple cider and brandy can also be produced by fermenting milled apple pulp. The possibility of making brandy from dried culled and surplus apples, grapes, oranges and other fruits have also been explored. Vinegar can also be prepared from fruit wastes. The fruit waste is initially subjected to alcoholic fermentation by acetic acid fermentation by Acetobacter aceti bacteria, which produce acetic acid. Vinegar production by fermenting waste from pineapple juice has been reported. Vinegar production by fermenting orange peel juice has also been attempted successfully. Apple pomace extract can also be mixed with molasses in the ratio of 2:1 for producing vinegar.
Single Cell Proteins
Single cell proteins can be produced from dried and pectin extracted apple pomace by using Trichoderma viride and Aspergillus niger. The grape waste and pressed apple pulp have also been employed as a substrate for Aspergillus niger to generate crude protein and cellulose. Pineapple waste for single cell protein production has also been utilized. Fusarium has been used for citrus peel juice to generate single cell protein. The waste from brewery and distilleries can also be used for the production of single cell proteins. Potato peels supplemented with ammonium chloride have also been used for the production of protein by using a non-toxic fungi Pleurotus ostreatus. Similarly, waste from orange, sugarcane and grape processing industry have also been utilized for the production of single cell protein.
Animal Feed
The waste obtained from processing of fruits and vegetables is rich in fibre, which includes cellulose, hemi-cellulose, lignin and silica with poor quality of protein. Fermented potato waste has been successfully tried as animal feed. Apple pomace after fermentation with different species yeast, followed by drying, makes the feed enriched with proteins, vitamins, minerals and fats and which can be used for feeding animals. Waste from wineries, breweries and distilleries can be used for feeding livestock. Animal feed can also be obtained from grape pomace after fermentation. Dry brewer's grains after addition of molasses become a very good cattle feed.
Alcohol
The waste from fruits and vegetable processing industries being polysaccharides (cellulose, hemi-cellulose and lignin) can be subjected to solid state fermentation for the production of ethanol, which has several uses. It can be used as a liquid fuel supplement and as a solvent in many industries. Process for production of ethanol from apple has been developed. Pear and cherry waste have also been utilized for production of ethanol. Orange peel after enzymatic hydrolysis was found suitable for the production of ethanol by use of Saccharomyces cerevisiae.
Biogas Production
Bio-mass consisting of agricultural, forest, crop residues, solid and liquid wastes from industries, sewage and sludge can be utilized for production of biogas through microbial technology. Similarly, the waste from fruit and vegetable processing industries has been used for production of biogas. Biogas is produced by anaerobic digestion of fruit and vegetable wastes. Methanotropic bacteria like Methanobacterium and Methanococus spp. can utilize CO2 from waste materials to produce methane. During this process, the complex polymers are first hydrolyzed into simple substances by acid forming bacteria and finally these are digested anaerobically by methanotropic bacteria and methane gas is liberated.
Organic acids
These acids are produced through aerobic fermentation of sugars. Since they are produced in large amounts they could easily be extracted and purified from the fermented medium. Grape pomace when used as a source of fermentation, approximately 10% of citric acid could be produced. Important organic acids produced by fermentation are citric, acetic and lactic acids which could be used in many processing factories like confectionary, synthetic beverages, alcoholic beverages. Apple pomace and mango peel have also been used for organic acid production
Enzymes
These biocatalysts are protein in nature and produced by fermenting the waste material with microorganisms. The extracellular enzymes are presenting the medium and intracellular enzyme remains in the cell after fermentation.Commercially, the three most important enzymes from fruit are papain (from papaya), bromelain (from pineapple) and ficin (from figs). Each is a protein-degrading enzyme used in such applications as meat tenderisers, washing powders, leather tanning and beer brewing. Mango peel, apple pomace,grape pomace, citrus pomace etc. are being used for production of enzymes such as pectinases, amylases , cellulases etc.
Fibre
It has been reported that processing waste such as peel, pomace etc generally contain up to 30% of fibre. It may be obtained by treating the waste with alkali followed by boiling with hydrogen peroxide in alcohol. The fibre is used to increase the nutritional value of confectionary products.
Starch
The starch content in the peel and pulp of most of the fruits and vegetables is very less (2-5% on dry wt. Basis). However, mango kernel contains up to 58% starch. It is used as the flour and also in the pharmaceutical industries for making many formulations.
Pectin
This is a gelling agent used in jams and some sweets found to a greater or lesser extent in most fruits. Commercially, pectin is extracted from citrus peel and apple pomace (the residue left after apple juice has been removed). Some other tropical fruits contain high levels of pectin, passion fruit being a notable example. The utilisation of the 'shells' remaining after pulp removal offers possibilities for pectin extraction.
Oils
The stones of some fruits (eg mango, apricot, peach) contain appreciable quantities of oil or fat, some of which have specialised markets for culinary or perfumery/toiletry applications. Palm kernel oil is well established as both cooking and industrial oil. In addition some seeds (eg grape, papaya and passion fruit) contain oil which has a much specialised market.
Anti oxidants
Solid wastes, produced from the processing of fruits and vegetables especially peel are rich source of biocolour and phenolic compounds with good antioxidant properties.
Above products from horticultural waste indicates that in some cases the value added by product may be more valuable than the main product. In fact the waste from one processing plant may be the raw material for another processing plant. In such cases utilization of waste rather than disposal should be the goal of the industry.

Ensilage
The processing wastes are highly seasonal and drying them is one of the effective ways of preservation. Like forage crops, ensilage from these wastes could be prepared and be used as animal feed. The peels from mango, orange and peas have been success fully ensilaged. The ensilaged material could also be used for the biogas production.
Composting
In recent years composting, which is essentially a traditionally biological method of dealing with lignocellulosic waste materials has been perceived as a viable option and it now ranks as a major biotechnological method of solid waste disposal. Under appropriate circumstances composting can be viewed as solution to two distinct but related problems, namely waste disposal and the need for recycling of organic matter in agriculture. In many countries composting is now being considered as more acceptable means of solid waste disposal than either dumping or incineration with their associated pollution problems.
Composting is basically a biodegradative process in which organic wastes are transformed and stabilized by the metabolic activities of a succession of mixed microbial population, each suited to the environment produced by the previous population. The compost made from fruit waste has been found to have better manure value than the farm yard manure.