Vegetable processing, Flower processing, Sago: waste characteristics, management, value addition

Processing (canning, drying, freezing, and preparation of juices, jams, and jellies) increases the shelf life of fruits and vegetables. Processing steps include preparation of the raw material (cleaning, trimming, and peeling followed by cooking, canning, or freezing. Plant operation is often seasonal

The vegetable processing industry typically generates large volumes of effluents and solid waste. The effluents contain high organic loads, cleansing and blanching agents, salt, and suspended solids such as fibers and soil particles. They may also contain pesticide residues washed from the raw materials. The main solid wastes are organic materials, including discarded fruits and vegetables. Odor problems can occur with poor management of solid wastes and effluents; when onions are processed; and when ready-to-serve meals are prepared.

Pollution Prevention and Control Reductions in wastewater volumes of up to 95% have been reported through implementation of good practices. Where possible, measures such as the following should be adopted:

• Procure clean raw fruit and vegetables, thus reducing the concentration of dirt and organics (including pesticides) in the effluent.

• Use dry methods such as vibration or air jets to clean raw fruit and vegetables. Dry peeling methods reduce the effluent volume (by up to 35%) and pollutant concentration (organic load reduced by up to 25%). Separate and recirculate process wastewaters.

• Use countercurrent systems where washing is necessary.

• Use steam instead of hot water to reduce the quantity of wastewater going for treatment (taking into consideration, however, the tradeoff with increased use of energy).

• Minimize the use of water for cleaning floors and machines.

• Remove solid wastes without the use of water.

• Reuse concentrated wastewaters and solid wastes for production of by-products. As an example, recirculation of process water from onion preparation reduces the organic load by 75% and water consumption by 95%. Similarly, the liquid waste load (in terms of biochemical oxygen demand, BOD) from apple juice and carrot processing can be reduced by 80%. Good water management should be adopted, where feasible, to achieve the levels of consumption. Solid wastes, particularly from processes such as peeling and coring, typically have a high nutritional value and may be used as animal feed.

Flowers come as waste from hotels, marriage gardens, temples, dargah and various cultural and religious ceremonies. However bulks of flowers are available from religious places (temples, dargah etc.) where they are used on daily basis thus making them a regular source of floral waste.

Flowers are considered as holy entities and hence are offered by pilgrims to their gods and goddesses. Every day these flowers offered by the devotees in temples are left unused and therefore become waste. This flower waste gets accumulated at religious sites like Temples, Mosques and Gurudwaras due to a number of religious practices and is also generated in places like Residential areas, Community centres, etc.

India is known for its festivities and has many occasions celebrated round the year when solid waste is generated like religious festivals and the cultural functions associated with them. This portion of community waste is generally neglected and requires due consideration. Because of our religious beliefs many of us avoid throwing flowers and other items which are used for prayers in the garbage and instead put them in the plastic bags and throw them directly in the water bodies, apart from this, it is also thrown near sacred trees with no suitable mode of disposal. For instance, Banaras, one of the holiest cities of the country, has no policy for the disposal of the tonnes of waste that comes from its many temples. Each day waste material weighing 3.5-4 tonnes is left behind in the city of temples. Such disposal of waste creates problems like eel and worm development, water pollution, foul odour, land pollution; moreover it is not good aesthetically.

Solid waste and littering can degrade the physical appearance of water bodies and cause deterioration of water quality. Degradation of floral waste is a very slow process as compared to kitchen waste degradation. Therefore there is a need of proper and ecofriendly process for floral waste treatment. Management and utilization of flower waste was carried out in some studies. One such example is the Kashi Vishwanath temple which draws maximum devotees all round the year, especially in the month of Shrawan, has its own system for the disposal of the hundreds of kilograms of waste resulting from offerings by devotees. Another case in point is the Vishwanath temple, where floral waste is converted into manure.

On an average 1,500 agarbattis (incense) can be made from one kg raw material (filling material as flower powder and binding material) through this technology. Flowers like genda are used to make incense sticks, while roses are converted to rose water. Besides incense and rosewater, the flowers can also be incorporated into herbal products such as herbal colours, natural dyes etc. The Temple Flower Project coordinated by Kalpvriksh is one such attempt which involves the use of waste flowers being thrown away by hotels and temples to make natural colour powders. It was inspired by the work done by Madhumita Puri of the Society for Child Development, Delhi.

 

Another case where floral waste management has yielded good pay offs is that of Ajmer Sharif Dargah of Khwaja Moinuddin Chishti where nearly 15 to18 Quintals of flowers, offered each day were used to be dumped in a well. Now, the flowers are not only recycled, but also generate employment for local women. With technical assistance from Central Institute of Medicinal and Aromatic Plant (CIMAP), Lucknow, the Dargah Committee has established a rose water distillation plant at the outskirts of Ajmer

Flowers have applications in many industries viz; perfumes, cosmetics, food, liquor and textile industries. Disposal of flowers in rivers, oceans, etc. leads to water pollution as well as affects the living organisms present in the waters.  Management of floral wastes by solid state fermentation for the conversion into different value-added products viz; compost; biofuels; biogas; bioethanol; organic acids; pigments; dyes; polyhydroxybutyrate-co-hydroxyvalerate production; food products; biosurfactants production; sugar syrup; incense sticks; etc. The floral waste is also a source for handmade paper production. These value-added products will have different applications; viz; compost can be used for various plant growth; biogas for electricity generation; food products as nutrients and additives. The dyes and pigments from floral wastes will have applications in various textile industries; while biofuels and bioethanol can solve the problem of energy crisis. The waste can thus be converted into wealth. The review highlights the industrial applications of value-added products obtained from the floral wastes.

The processing of cassava tubers yields the following by-products that can be valuable livestock feeds when properly processed.:

·                    Cassava peels can represent 5 to 15% of the root. They are obtained after the tubers have been water-cleansed and peeled mechanically. They may contain high amounts of cyanogenic glycosides and have a higher protein content than other tuber part..

·                    Cassava pomace, also called cassava fibre, cassava bran, cassava bagasse, cassava starch residue and cassava pulp: all these terms refer to the solid fibrous residue (up to 17% of the tuber) that remains after the flour or starch content has been extracted.. The quality and appearance of these residues vary with plant age, time after harvest and industrial equipment and method used.

·                    Cassava sievate or garri sievate is the by-product of the production of garri (also spelled gari or gary), a popular West African food. Tubers are peeled, crushed and then fermented. The resulting product is then sieved and roasted. The sievate represents 15-17% of the root in weight).

·                    Cassava stumps are the ends trimmed off the cassava tubers as they are manually prepared for onward transmission into the rotary washer and peeler.

·                    Cassava whey is the liquid pressed out of the tuber after it has been crushed mechanically. The whey and the pomace may be mixed together to form an effluent (or slurry).

·                    Discarded tubers: tubers that fail to meet quality standards for processing are discarded and can be used for animal feeding. Discarded tubers are sometimes still attached to the peduncle and therefore may contain more fibre. They may also be mixed with the stumps.

Processes 

Cassava peels

Fresh cassava peels have 3 main deficiencies: they spoil very quickly, they contain phytates and large amounts of cyanogenic glycosides. They should thus be processed in order to reduce cyanogenic potential and phytate content and to preserve their nutritive quality. Different processes are effective in reducing cyanogenic glycoside including sun-drying, ensiling, and soaking + sun-drying. All these methods have yielded satisfactory results,

Good quality silage can be obtained after chopping the peels to equal lengths of about 2 cm for easy compaction, and wilting for 2 days to reduce moisture content from 70-75% to about 40%. Under these conditions, cassava peel silage after 21 days was light brown in colour, firm in texture and had a pleasant odor. The pH was 4.4, and no fungal growth was observed.

In Nigeria, drying cassava peels on black plastic sheets has been drawing the attention of smallholders and was the winning project of the 2008 Global Development Marketplace (a grant program held by the World Bank): "Using cassava waste to raise goats"

Solid fermentation of a mixture of cassava peels and waste water from fermented cassava pulp with Saccharomyces cerevisiae and Lactobacillus spp. resulted in a product with a higher protein content, lower cyanogenic glycosides and lower phytate content.

Cassava pomace

Cassava pomace (also called bagasse, bran or pulp) contains less cyanogenic glucosides than the peels. It can be dried or ensiled. To ensile, cassava pomace is ground with the addition of either 0.5% salt (on fresh weight basis) or rapidly fermentable carbohydrates, such as ground maize or molasses, before being placed in anaerobic conditions in pits or plastic bags. Addition of urea and minerals is also possible.

Environmental impact 

Cassava processing produces large amounts of waste and is generally considered to contribute significantly to environmental pollution. A cassava starch production unit processing 100 tons of tubers per day has an output of 47 tons of fresh by-products, which may cause environmental problems when left in the surroundings of processing plants or carelessly disposed of . In Nigeria, for example, cassava wastes are usually left to rot away or burnt to create space for the accumulation of yet more waste heaps. The heaps emit carbon dioxide and produce a strong offensive smell. Cassava peels (large amounts of cyanogenic glucosides) and pomace (large amounts of biodegradable organic matter) may cause surface water pollution especially if they are stored under heavy rain or simply disposed of in surface waters . The presence of a large processor or several small processors can cause the eutrophication of slow moving water systems, notably during the dry season. However, cassava processing does not seem to affect groundwater supply, except occasionally in the immediate surroundings of processing units, due to leaching through the soil. Starch extraction requires large volumes of water and may cause water depletion, but in most areas this problem is minimized by the adoption of processing technologies suitable for the water resources available.

Nutritional attributes 

Cassava peels

Cassava peels have a low protein content (< 6% DM) and a high and variable fibre content (crude fibre in the 10-30% DM range).

Cassava pomace

Cassava pomace is a highly variable by-product as its composition is driven by the starch extraction technology used in the processing plant. Its protein content is very low (1-4% DM). Starch content can vary between 15 and 50% DM and NDF content is more than 35% DM. Fresh cassava pomace contains mostly water (75-85%).

Potential constraints 

Cyanogenic potential

Cassava contains 2 cyanogenic glycosides, linamarin (80% of total glycosides) and lotaustralin (20%), which are acted upon by a cell-wall enzyme to liberate hydrogen cyanide (HCN), which is lethal to animals. HCN is then released when the cell-wall is broken (eaten or processed). Hydrogen cyanide concentrations depend on cultivar, environmental conditions, plant age, number of harvest (for the foliage) and on the plant component that is being considered. There is a continuous gradient of HCN content between varieties, which are usually divided into two groups:

·                    Bitter varieties with roots containing 0.02-0.03% HCN (DM basis) and leaves containing up to 0.2% HCN (fresh basis). These have to be processed before being used as feed.

·                    Sweet varieties with roots containing less than 0.01% HCN (DM basis) and leaves 0.1% HCN (DM basis). These can be fed raw. Most commercial varieties belong to this group.

Bitter varieties have often longer and thicker roots than the sweet varieties, but there is no simple and safe method to assess HCN content. However, HCN can be relatively easily removed from cassava by-products, as shown in Processes on the "Description" tab. Well-processed cassava peels have generally acceptable levels, below 50 mg/kg. However, mass HCN poisoning has been reported in a intensively managed Nigerian pig farm, where more than half of the herd died within a few hours after consuming boiled and overly ripe cassava peels from a bitter variety. Treating the surviving pigs with antibiotics and palm oil saved some of them.

Phytate content

Cassava peels have a high phytate content (up to 1% DM), resulting in low P availability in non-ruminants. Fermentation can slightly reduce phytate content (down to 0.7%).