COMPOSTING OF TANNERY WASTE WITH SAWDUST FOR PRODUCTION OF ORGANIC MANURE

ABSTRACT

The utilisation of tannery waste (TW) in combination with sawdust (SD) as compost manure for agricultural use was studied. The two wastes samples were collected and mixed in the ratios (TW/SD) 1:1, 1:5, 5:1, 1:10 and 10:1, respectively. Composting bin was used during the process. The composting was done for 6 weeks under aerobic condition  with  frequent  turning  for  proper  aeration.  Microbiological  and physicochemical parameters of the samples (tannery waste and sawdust), experimental soil (SL), as well as the finished compost were determined using standard methods. The microorganisms isolated from the wastes (TW, SD and SL) were species of Bacillus, Escherichia, Micrococcus, Proteus, Pseudomonas, Streptococcus, Staphylococcus (bacteria) Aspergillus, Mucor, Tricophyton, Rhizopus, Penicillium, Fusarium, Candida and Saccharomyces (fungi). The resultant compost was obtained 42 days after being composted; it was odourless, stable and had earthly smell. The pH of the matured compost ranged from 7.30 to 8.05 (moderately alkaline), total organic carbon (14.84% to 24.33%), carbon to nitrogen ratio ranged from 10.96 to 31.46, phosphorus content (2.55 to 3.48%), potassium content (0.961 to 2.912%) and heavy metals such as (Cr, Pb, Cd, Zn, Hg, Fe, Mg) were within the permissible limits for matured quality compost. The germination index (emergence) was significantly high (p<0.05) in all treatments including the control. The resultant compost was used to assess the growth parameters (leaves, height and stem girth) and yield performances of maize plants. Maize plants treated with compost (TW/SD 1:1), supported good growth pattern as well as seed formation, while maize plants treated with compost (TW/SD 1:10) had poorest response which resulted in stunted growth with smaller leaf sizes as well as narrowest stem girth. Compost (TW/SD 10:1) supported good growth pattern of the maize plants with significant increase in height, stem girth and leaf length (with extensive leaf sizes and greenish). This suggests that the nutrient content of the compost (TW/SD 10:1) was utilized by the plants for their growth. Height of maize treated with TW/SD 1:1 on maize was not significantly (p>0.05) different from Amazing organic fertilizer (commercial). The yield of maize was obtained 102 days after planting. The mean yield of maize raised with the compost TW/SD ranged from 0.4±0.05kg to 1.5±0.01kg. The highest yield of 1.5±0.01kg obtained with TW/SD 1:1 was significantly different (p<0.05) from TW/SD 10:1. The results obtained suggest that tannery waste/sawdust compost in the right combination can be applied for the improvement of soil organic matter and boost food production.

CHAPTER ONE

1.0  INTRODUCTION

1.1 Background to the Study

Composting of organic waste is a bio-oxidative procedure comprising partial humification  of  organic  matter  and  mineralisation,  producing  stabilised  finishing product known as compost, free from pathogens, phytotoxicity and humic properties (Elnasikh and Satti, 2017). It is an aerobic biological method which utilizes naturally occurring microorganisms to convert biodegradable organic matter into humus-like product. The aerobic composting is the process of disintegration of organic substrates in the presence of oxygen which powers microbial action (Nwankwo et al., 2014). The procedure destroy pathogens,  transforms  nitrogen from  unstable  ammonia to  stable organic forms, minimizes the quantity of the waste and enriches the nature of the waste (Agyarko-Mintah et al., 2016). During composting process diverse microbial communities obliterate organic matters into simpler nutrients. It may be supplementary effective when the moisture content is exact according to material of the compost, and the carbon to nitrogen ratio (Batham et al., 2013).

Compost is made by decaying any organic materials such as sawdust, domestic garbage, straw, lawn dipping, and plant materials (Argun et al., 2017). It has dual exceptional effects on soils, essentially on nutrient deficient soils. It replaces the missed soil organic constituents and provides plant nutrients (Olowoake et al., 2018). Naturally, compost use to soil affects both variety as well as size of microbial populations with enzyme actions, as majority of the processes in soil are facilitated by enzymes from microbial source  (Weerasinghe  and  De  Silva,  2017).  Conversely,  the  enhancement  of  soil microbes  as  well  influences  plant  growth  through  the  presence  of  plant  growth promoting  hormone  and  rise  of  nutrient  accessibility.  Additionally,  compost  can improve crop yields due to nutrient release during disintegration and mineralization (Weerasinghe and De Silva, 2017).

Composting and co-composting are among the native procedures obtainable for the removal of solid waste  pollution merged with resource renewal through stabilizing mixed types of organic wastes (Anwar et al., 2015). As in the production procedures, the application of large-scale composting fetches better economic advantages. Co- composting of other than a single type of waste can be a more feasible management process of solid wastes (Anwar et al., 2015). It is a technique of handling many brands of organic wastes. Most extensively used co-composted ingredients are animal waste product with agro-wastes for example stalk, rice straw, sawdust, corn stalk, wheat straw (Anwar et al., 2015). The adding of bulking agent for composting heightens substrate properties such as air space, pH, moisture content, carbon-to-nitrogen (C:N) ratio, mechanical structure and particle density, affecting entirely the disintegration rate (Anwar et al., 2015). Composting has been frequently acknowledged as an environmental friendly alternative approach of recycling organic solid wastes (Ijah, 2006; Ezeagu et al., 2017a). Additionally, making good soil amendment, composting is a unique method of reducing the quantity of wastes that are sent to landfills, burnt or left in a way that cause contamination of land or water bodies. These wastes, which were one time put in the landfills, have gradually been prepared into useful products. Therefore, composting can be a skill of choice for the conversion of tannery solid wastes into a compost material with a high agronomic value, especially in the instance of dehairing wastes, where the concentrations of heavy metals are less. Currently, there is little information concerning composting of tannery waste with sawdust as an organic amendment.

Bulking agents are augmented in the composting course for different reasons as energy source for microbes, proper air circulation through the mixed wastes by enhancing porosity,  appropriate  absorption  and  to  heighten  the  degradation  of  composting materials (Zhou et al., 2014). Sawdust is a by-product of cutting, drilling, grinding, sanding, or else crushing wood with a saw or other tool; it is made of fine particles of wood. Therefore, is a carbonaceous organic substance which has a very rich carbon to nitrogen ratio (Betham et al., 2013). The sawdust is cheap and common accessible bulking  agent.  Thus,  it  holds  potential  as  contributing  to  the  carbon  source  for increasing soil organic matter when applied. It is a very frequent bulking agent utilized in composting which furnishes the free air space, moisture control and retain the carbon to nitrogen ratio (Zhou et al., 2014).

Tanning involves the handling of hides and skins to transform and maintain them into leather which will be preserved and fit for various brands of applications (Mohammed et al., 2017). The use and unusable hides and skins in proportion to the excess process chemicals and water comprise liquid and solid wastes in the tannery (Mohammed et al., 2017). There are different modes of tanning system which include; the chrome tanning as well as vegetable tanning (does not involve chromium). In the treatment of raw hide and skin, sulphuric acid and salt are employed, and later treated with the solution of chromium salts. In the tannery, chromium, hydrochloric acid, formic acid, sulphuric acid, caustic potash, caustic soda, arsenic sulphate, sodium arsenite, soda ash are used for numerous tanning processes such as liming, de-liming, soaking, tanning  (Tinni et al., 2014).  Also vegetable tannins are applied to re-tan leather particularly at the local tanning level by the application of plant materials (such as the pods, tree bark) which comprises condensed or hydrolysable tannins (Tijjani, 2014).

1.2 Statement of the Research Problem

The chemical fertilizers are expensive and cause harm to the environment. Besides, not all farmers can get access to chemical fertilizers. Tanneries and wood industries in the country are growing and both produce a lot of wastes. Often these wastes are dumped unattended, and thus result in polluting the environment producing horrible odour especially the tannery waste. The wastes (tannery and sawdust) are abundant in areas dominated by tanning and wood work activities constituting waste disposal problem. However, the wastes can be converted to useful products.

1.3 Justification for the Study

Extensive use of soil for years, combined with wrong use of agro-chemicals, has generated in many locations leading problems of soil nutrient degradation and heavy metal contamination in most of Nigerian soils. Therefore, there is the need to lessen environmental problems by using cheaper organic manure obtained through bioconversion of toxic industrial waste. Tannery waste and sawdust can be converted into compost which is very useful in agriculture. Most of these wastes are organic in nature which means they are biodegradable. Studies establish that the fundamental to sustainable agricultural production and long term productivity of agro-ecosystems are procedures that conserve organic matter in the soil (Dinesh et al., 2012).

The present work was focused on making compost from tannery waste combined with sawdust as bulking agent. Recycling of organic wastes such as tannery wastes for agricultural use become very necessary so as to be adopted or used where poor quality soils exist (with depleted nutrients) and reduce over dependency on chemical fertilizers; which can result in soil health problems. The use of compost improves soil structure, water  permeability  and  soil  fertility.  Organic  amendments  can  also  promote  plant health, and even increase yields.

1.5 Aim and Objectives of the Study

The aim of the study was to convert tannery waste into organic manure by composting with sawdust. The objectives of the study were to:

i.      determine the microbiological and physicochemical properties of tannery waste, sawdust and soil

ii.      characterise and identify the microbial isolates

iii.      produce organic manure from tannery waste using sawdust as bulking agent iv. characterise the organic manure produced

v.         determine the efficacy of the organic manure produced in the field using maize as a test crop

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