Analysis of the Physico-chemical Characteristics of Brewers Spent Grain (BSG)

Brewer’s spent grains are byproducts produced in large quantities from the brewing industry. Characterizing agro-industrial wastes is an important step to add value and increase its viability for various applications. In this experiment, the physico-chemical characteristics of Brewers Spent Grain (Total solids, volatile solids, organic carbon, total nitrogen) were analyzed. (APHA, 1999) standard was used to analyze the characteristics. The results revealed that, BSG has a total and volatile solid content of 94.95 and 90.04 %, respectively. The carbon to nitrogen ratio of brewer’s spent grain was 13.91. After pre-treatment the moisture content and ash content were found to be 5.05% and 10.96% respectively. It was shown that BSG exhibits higher variations according to barley variety, planting time and mashing process in the factories. Keyword : BSG, total solid, volatile solid, Carbon to nitrogen ratio DOI: 10.7176/JNSR/11-18-02 Publication date: September 30 th 2020

Despite its potential as a valuable and renewable resource for industrial exploitation, it has received little attention as a marketable product yet. Its chemical composition (high nitrogen content, fibres,) makes BSG very useful for the production of high-added-value input in the industrial sector.
In order to utilize as a value-added input or utilization in the biotechnology industry it is important to characterize physicochemical characteristics of BSG.
2. Methodology 2.1. Determination of the characteristics of BSG 2.1.1. Total solids (TS) Sample BSG was weighed in a crucible using electrical balance. 5 g of each sample was weighed and placed inside an electric hot air-oven maintained at 105 o C. The crucible is allowed to remain in the oven for 24 hours, and then taken out, cooled in a desiccator, and weighed (APHA, 1999). The weight of the sample, which was left in the oven, gives the total solids and it is represented in percentage basis. % TS = * 100 Where, m1 = Initial weight m2 = Mass after evaporated in oven % TS = percentage total solid 2.1.2. Analytical Procedure for VS The volatile solids (VS) in organic wastes are measured as total solids minus the ash content, as obtained by complete combustion of the feed wastes. Volatile solid contains largely carbon, oxygen and nitrogen that burn off an already dry sample in a laboratory furnace at 500-600 o C, leaving only the ash which contains largely calcium, magnesium, phosphorus, potassium and other mineral elements that do not oxidize. The VS content was determined as follows. After determining the final weight in total solids analysis, the respective cooled oven dried BSG sample was placed in a muffle furnace and ignited at 550°C for exactly 5hrs.
The muffle furnace dried sample was then placed and kept in desiccator for an hour. Immediately after samples were allowed to desiccate, it was weighed in the sensitive analytical measuring balance. Then the following formula was applied to calculate the percentage of volatile solid content of the TS (APHA, 1999).
VS % = * 100 Where, m1 = Initial weight m2 = Mass of sample after evaporated in the oven m3 = Mass after ignition at 550oC, % VS = Percentage of volatile solids Fixed solids (FS) It is the mass of the ash remaining after ignition at 550 o C. = + 2.1.3. Organic Carbon determination An estimate of the amount of carbon in a feedstock component can be calculated from the Volatile Solids (VS) content of the dried material. The percentage composition of carbon can be calculated by applying the following equation as described by (Haug, 1993). % Carbon = % .

* 100 2.1.4. Nitrogen determination
The total nitrogen of sample BSG was determined by the Kjeldahl procedure. Digestion of the organic material was performed by the addition of concentrated sulphuric acid to 1g sample of feed stocks in the digestion tube. It was heated at 370 o C by the addition of Selenium as a catalyst for the digestion process. The solution was distilled with 1.5 N NaOH solution that can convert the ammonium salt to ammonia. The amount of ammonia present in the sample was determined by titrating it in boric acid. The boric acid captures the ammonia gas. Finally, the amount of nitrogen in a sample can be calculated from the quantified amount of ammonia ions in the receiving boric acid solution (APHA, 1999). Finally, the carbon to nitrogen ratio of each treatment is calculated by applying simple mathematics as: C: N = % %

Characteristics of the feed stock
The total solid and volatile solid contents of BSG was found and summarized as follows.
Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.11, No.18, 2020  The total solid content of brewer's spent grain is 94.95%. It consists of a volatile solid and ash content of 89.04 % and 10.96 % respectively. This shows that a large fraction of BSG is biodegradable. This shows, BSG has high potential for utilization as biodegradable substrate for various biotechnology and industrial applications. The total solid content of BSG in this study is far more than that reported (17.6 ± 5) by (Kivaisi & Mukisa, 2000). This wide difference was observed due to pretreatment in this study has reduced its moisture content to a significant level; whereas the volatile solid content of 89.04 % is in accordance with a value of 90.7 ± 4.7 %. This value (89.04) is in the range of 70 to 90% for different feed stocks as described by (Steffen, et al., 1998).  Table 3.2 shows the C: N ratio of brewers' spent grain is 13.9 %. The carbon content of BSG was 53 % which is higher than that reported by (Khidzir, 2010) as 35.6 ± 0.3 %. (Uzodinma, 2007), reported a carbon content of 47. 2% which is a bit lower than the result of this study.

Carbon and Nitrogen content of BSG
The total nitrogen content of BSG obtained in this study (3.81 %) is in between the values 1.025 ± 0.05% and 4.53 % as reported by (Khidzir, 2010) and (Ezekoye, 2009) respectively.
According to (Xiros & Christakopoulos, 2009), the chemical composition of BSG varies according to barley variety, harvest time, malting and mashing conditions, and the quality and type of adjuncts added in the brewing process and hence the physicochemical characteristics of BSG varies and there is a value range for data of several BSG characteristics.

Conclusion
Increasing efforts are being directed towards the reuse of agro-industrial by-products, from both an economic and environmental viewpoint. BSG is plentiful by-product produced in breweries worldwide. Physicochemical analysis revealed that there is higher total solid and volatile solid amount in BSG. This makes BSG ideal for various biotechnology applications and anerobic digestion.