Efficacy and profitability of a mobile grinder system for biomass production in Korea

Figures & data

Figure 1. Tub grinder (DuraTech 3010T) and grapple excavator loader (Daewoo Solar 200W).

Table 1. Specification of the grinder and loader used for mobile grinder system in Korea.

Grinder	Duratech 3010T	Loader	Daewoo Solar 200W
Weight	20.2 ton	Weight	19.2 ton
Transport length	11.07 m	Overall length	9.29 m
Transport width	2.59 m	Overall width	2.49 m
Transport height	3.45 m	Overall height	3.74 m
Ground clearance	0.338 m	Bucket capacity	0.750 m^3
Engine power	354.2 kW (475 HP)	Engine power	107.4 kW (144 HP)
Fuel capacity	605.6 liter	Fuel capacity	300 liter
Hammers	20 fixed single bolt or 40 swinging
Hammer rods	Eight 38.1 mm × 1.09 m long
Screens	Split screens 25.4 mm thick in various sizes
Screen area	1.57 m^2

Note: DuraTech Industries (2014)

Table 2. Definition of work elements for the mobile grinder system.

Non-productive/productive work time	Work element	Definition
Non-productive work time	Preparation and positioning	Checking and starting up grinder and loader, and moving them to adequate position
Productive work time	Grabbing	Grabbing woody material with a grapple
	Grapple swing	Swinging a grapple with woody material to feed into grinder
	Feeding	Feeding woody material into grinder
	Helping in feeding	Pressing woody material into grinding tub and clearing debris around the grinding area for next feed-in
	Booming out	Booming out a grapple to grab woody material
Non-productive work time	Fueling and knife change	Fueling the loader/grinder and changing the knives of the grinder

Table 3. Work time and productivity per cycle and day (values in parentheses are standard deviation).

Measurement	Cycle	Day*
Productive work time (min)	79.1 (± 3.34)	237.4
Non-productive work time (min)	36.7 (± 2.79)	110.1
Total work time (min)	115.8	347.5
Production capability (m^3)	151.6^†	454.9
Estimated productivity (m^3)	82.1	246.2^‡

Note: The mobile grinder system consists of a three-man crew. *Day consists of three cycles. ^†Based on 115 m³/h for brushes and shrubs (Shinyoung Equipment Solutions 2016). ^‡Daily production was 160 tons (160 tons / (0.65 ton/ m³) = 246.2 m³) (personal communication with grinder operators 2014).

Table 4. Work time by work element and cycle.

		Work time by element
Non-productive/productive work time	Work element	Mean (s)	SD* (s)	Percent (%)	Work time per cycle (min)
Non-productive work time	Preparation and positioning	NA^†	NA	NA	11.4
	Grabbing	12.9^a	8.0	23.8	18.9
	Grapple swing	8.8^b	4.1	16.3	12.9
Productive work time	Feeding	4.1^c	1.6	7.7	6.1
	Helping in feeding	19.9^a	25.5	36.9	29.2
	Booming out	8.3^b	5.6	15.3	12.1
	Total	54.1	NA	100.0	79.1
Non-productive work time	Fueling and knife change	NA	NA	NA	25.3

Note: Grinding production times per cycle were calculated by multiplying percent and the total productive work time from Table 2 (79.1 min). *Standard deviation. ^†Not available. Superscript letters (a, b, and c) next to means represent significant difference at α = 0.01.

Table 5. Itemized daily rental cost of the mobile grinder system.

		Daily cost
Item	Detail	W/day	US$/day*
Fuel	7 0 liter/h × 8 h/day × W1750/liter	980,000	930
Loader rental	Grapple excavator	650,000	617
Knife (supplies)	2 0 units/set^† × W30,000/unit	600,000	570
Labor	W200,000 (grapple excavator operator) + W150,000 (senior worker) + W80,000 (junior worker)	430,000	408
Maintenance	Machine oils, compressor, trailer costs	1,000,000	949
Other fees	Insurance, management fee	340,000	323
Total		4,000,000	3798

Note: Based on NFCF in Daejeon, Korea (computer printout, 2014). *Converted from Korea Won based on 2014 currency exchange rate (KEB Hana Bank 2016). ^†A set of grinder knives that consists of 20 individual knives was needed daily.

Table 6. Profitability of the mobile grinder system using the production capability.

	Unit price	Daily production/cost
Item	W/m^3	W/day	US$/day*
Grinding production for sawdust and wood wastes	41,330^†	+18,802,670	+17,853
Rental cost of the mobile grinder system		–4,000,000^‡	–3798
Loading cost (hardwood)	4600^§	–2,092,724	–1987
Transportation cost (hardwood, 100–200 km distance, 25 ton truck)	15,800^§	–7,188,052	–6825
Total		+5,521,894	+5243

Note: Based on the production capability from the manufacturer (Shinyoung Equipment Solutions 2016). *Converted from Korea Won based on 2014 currency exchange rate (KEB Hana Bank 2016). ^†Market sales price from NFCF (2014). ^‡Table 5. ^§KOFPI (2014).

Table 7. Profitability of the mobile grinder system using the estimated productivity.

	Unit price	Daily production/cost
Item	W/m^3	W/day	US$/day*
Grinding production for saw dust and wood wastes	41,330^†	+10,173,538	+9660
Rental cost of the mobile grinder system		–4,000,000^‡	–3798
Loading cost (hardwood)	4,600^§	–1,132,308	–1075
Transportation cost (hardwood, 100–200 km distance, 25 ton truck)	15,800^§	–3,889,231	–3693
Total		+1,152,000	+1094

Note: Based on the estimated productivity from the interviews with grinder operators. *Converted from Korea Won based on 2014 currency exchange rate (KEB Hana Bank 2016). ^†Market sales price from NFCF (2014). ^‡Table 5. ^§KOFPI (2014).

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