Enhancing the fuel properties of beverage wastes as non-edible feedstock for biofuel production

Figures & data

Figure 1. (a) spent coffee ground (SCG) (b) brewery spent grain (BSG).

Table 1. The higher heating value (HHV) of some substrates.

Substrate	HHV (MJ/kg)
Wood	10–20
Wood pellet	20
Briquette	18.5
Sawdust	12
Vineyard pruning	14–18
Rice husk	12–14
Red maple (RM)	19.32^a
Torrefied red maple	28.11^a
Mixture of RM + Coal	25.85^a
Torrefied yellow poplar	26.44^a
Coal	28

^a Data from Singh and Zondlo [24].

Table 2. Proximate analysis results for biomass substrates.

Sample	Moist%. % (%)	Ash% %(%)	VM% %(%)	FC% %(%)	Total
BSGI	81.8	3.82	9.92	4.46	100
SCGI	57.7	0.90	35.06	6.34	100
BSGE	76.2	3.16	13.8	6.84	100
SCGE	60.3	1.56	29.7	8.44	100
BSG60SCG40I	70.71	2.43	18.31	8.55	100
BSG50SCG50I	70.28	0.98	18.44	10.3	100
BSG40SCG60I	67.91	0.90	21.59	9.6	100
Biomass^a	2.5–62.9	0.1–34.3	30.4–79.7	6.5–35.3
Coal^a	0.4–20.2	15–48.9	12.2–44.5	17.9–70.4

^a Data for biomass and coal reported by Singh and Zondlo [24]. VM % = A-moist. %, FC =  100 − (moisture % +-Ash % + VM %), I; IC LAB LJMU (all samples werecollected November 2019), E; externally certified laboratory SOCOTEC (all samples were collected March 2020). Samples were analysed at least 3 times to assure reproducibility, using approximately 1 g each under the required conditions. Data represent statistical differences at a 95% confidence level (p ≤ 0.05).

Table 3. Comparison of data from the proximate analysis of spent coffee grounds (SCG) and brewery spent grain (BSG) with values reported in the literature.

Parameter	Qty in % wt. (present study) SCG	Qty in % wt. (literature) SCG	Ref.	Qty in % wt. (present study) BSG	Qty in % wt. (literature) BSG	Ref.
Moisture content	57.7–60.3	60 3.60 60.6 57.6 6.09	(a)	76.2–81.8	75–85 82.6 ± 0.10	(b)
Ash content	0.9–1.56	0.50 2.2 1.8	(c)	3.16–3.82	2.3–7.9 2–5 3.8 ± 0.00	(d)
Volatile matter	35.06	84.86	(e)	13.8	83.4 ± 2.8	(f)
Fixed carbon	8.44	56.1 13.85	(g)	6.84	42.5 ± 2.5	(h)
Heating value	23.5 MJ/kg	23.4 MJ/kg	(i)	22.7 MJ/kg	27.0 MJ/kg	(j)

(a) [30, 33–35]

(b) [36–38]

(c) [30, 39–41]

(d) [16, 29, 35]

(e) [33]

(f) [42]

(g) [33]

(h) [43]

(i) [43]

(j) [35, 44]

Table 4. Elemental analysis of dried, and dry ash-free samplesof biomass substrates, compared with commercially available biomass substrate/fuels.

Substrate	Carbon	Hydrogen	Nitrogen	Sulphur	Oxygen (100-CHNS)
BSG AA	42.7 ± 7.1	4.5 ± 1.7	2.7 ± 0.2	0.18 ± 0	49.92
SCG AA	43.4 ± 7.6	4.8 ± 1.9	2.0 ± 0.4	0.12 ± 0.03	49.68
BSG D	51.2 ± 0.1	5.4 ± 1.4	3.3 ± 0.1	0.23 ± 0.01	39.87
SCG D	54.2 ± 1.1	5.8 ± 1.3	2.5 ± 0.04	0.15 ± 0	37.35
BSG AF	53.6 ± 0.1	5.7 ± 1.5	3.5 ± 0.1	0.24 ± 0.01	36.96
SCG AF	55.5 ± 1.2	5.9 ± 1.3	2.6 ± 0.04	0.15 ± 0	35.85
Barley	41.59^b	6.08^b	1.79^b	0.35^b	50.18^b
Coffee husk	45.06^b	6.42^b	2.53^b	0.48^b	45.51^b
Saw dust	45.34^b	6.02^b	0.53^b	1.07^b	47.05^b
Briquette	46.74^b	6.39^b	1.24^b	0.10^b	45.52^b
Vegetal coal	79.34^b	2.74^b	0.65^b–2.8^a	0.30^b	16.97^b

AA: Sample as analysed. D: Dried sample dried. AF: Ash-free dried sample. Data represent statistical differences at a 95% confidence level (p ≤ 0.05).

^a Value reported by Singh and Zondlo [24].

^b Value reported by García et al. [51].

Figure 2. BSGAA- brewery spent grain sample as analysed SCGAA-spent cofee ground sample as analysed BSGD-brewery spent grain sample dried SCGD-spent coffee ground sample dried BSGAF-brewery spent grain sample ash-free dried SCGAF-spent coffee ground sample ash-free dried.

Table 5. Phenolic content analysis for spent coffee grounds (SCG) and brewery spent grains (BSG).

Determinand	MDL	SCG1 (mg/kg)	SCG2 (mg/kg)	BSG1 (mg/kg)	BSG (mg/kg)
2,4,5-trichlorophenol	0.1	2	2	2	2
2,4,6-trichlorophenol	0.1	2	2	2	2
2,4-dichlorophenol	0.1	2	2	2	2
2,4-dimethylphenol	0.1	2	2	2	2
2,4-dinitrophenol	0.5	10	10	10	10
2-chlorophenol	0.1	2	2	2	2
2-methylphenol	0.1	2	2	2	2
2-nitrophenol	0.1	2	2	2	2
3,4-methylphenol	0.1	0.2	0.2	0.2	0.2
4,6-dinitro-2 methylphenol	0.2	4	4	4	4
4-chloro-3-methylphenol	0.1	2	2	2	2
4-chlorophenol	0.5	10	10	10	10
4-nitrophenol	0.5	10	10	10	10
Pentachlorophenol	0.5	10	10	10	10
Phenol	0.1	2	2	2	2
Total phenolic content		62.2	62.2	62.2	62.2

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