Total Fuel-Cycle Analysis of Heavy-Duty Vehicles Using Biofuels and Natural Gas-Based Alternative Fuels

Figures & data

Figure 1. Upstream and downstream stages of the TFC for conventional and alternative fuels.

Figure 2. Six fuel pathways analyzed for the HDV sector.

Table 1. Fuel specifications

	ULSD	BD20	ED10	FTD100	CNG	LNG
Fuel composition	100% ULSD	80% ULSD, 20% BD	89% ULSD, 10% ethanol, 1% additive	100% natural gas-based FTD	100% CNG	100% LNG
Sulfur content ^a (ppm by weight)	15.0	12.0	13.7	0.0	6.0	0.0
Carbon content ^b	87.1%	85.2%	83.6%	85.3%	72.4%	75%
Lower heating value (Btu/gal or btu/ft3) ^b	129,488	127,500	124,038	123,670	983	74,720
Mass density (g/gal or g/ft3) ^b	3,206	3,237	3,180	3,017	22	1,621
Fuel economy ^c (mpg)	5.9	5.9	5.6	5.9	4.7	4.7
Efficiency (mi/MBtu)	45.6	45.8	42.9	45.4	36.1	36.4
Notes: ^aSulfur content for neat fuels are from the fuel specifications section of GREET, except for ULSD, which is assumed as 15 ppm to meet on-road diesel standards. Sulfur content for mixed fuels are calculated based on the ULSD baseline and composition ratio. ^bFrom GREET fuel specifications. ^cULSD fuel economy rating from the National Renewable Energy Laboratory12; rating of other fuels calculated using each fuel's energy content relative to ULSD and estimated efficiency values from the literature.2,57,59 The assumed efficiency differences are as follows: BD20 (+0.5%), ED10 (−6.0%), FTD (−0.3%), CNG (−20.7%), and LNG (−20.2%).

Table 3. Results from HDV TFC analysis for energy use, petroleum consumption, and select emissions

Item	Feedstock Stage	Fuel Processing Stage	Vehicle Use Stage (Tailpipe EFs)	Percent Vehicle Use Stage	Total	Ratio of Alternative Fuel Total to ULSD
ULSD
Total energy (Btu/t-mi)	60	120	1095	86	1280	–
Petroleum (Btu/t-mi)	10	60	1095	94	1170	–
CO2 (g/t-mi)	5	10	85	86	100	–
CH4 (mg/t-mi)	90	10	<1	<1	100	–
N2O (mg/t-mi)	<1	<1	<1	52	<1	–
GHGs (g/t-mi)	10	10	85	84	105	–
VOC (mg/t-mi)	5	5	15	65	20	–
CO (mg/t-mi)	5	5	230	95	240	–
NOx (mg/t-mi)	20	15	470	93	505	–
PM10 (mg/t-mi)	<1	5	5	39	10	–
SOx (mg/t-mi)	5	10	<1	5	15	–
BD20
Total energy (Btu/t-mi)	100	405	1090	69	1590	1.25
Petroleum (Btu/t-mi)	35	50	840	91	925	0.80
CO2 (g/t-mi)	−5	10	85	98	90	0.90
CH4 (mg/t-mi)	80	15	<1	<1	90	0.90
N2O (mg/t-mi)	<1	<1	<1	9	<1	NA
GHGs (g/t-mi)	−5	10	85	95	90	0.90
VOC (mg/t-mi)	5	20	15	35	40	2.00
CO (mg/t-mi)	10	5	215	94	230	0.95
NOx (mg/t-mi)	25	15	490	92	530	1.05
PM10 (mg/t-mi)	<1	5	5	30	10	1.00
SOx (mg/t-mi)	15	10	<1	4	25	1.65
ED10
Total energy (Btu/t-mi)	80	205	1165	80	1455	1.15
Petroleum (Btu/t-mi)	20	60	1080	93	1160	1.00
CO2 (g/t-mi)	<1	10	85	87	100	1.00
CH4 (mg/t-mi)	90	15	<1	<1	110	1.10
N2O (mg/t-mi)	5	<1	<1	8	<1	NA
GHGs (g/t-mi)	5	10	85	84	100	1.00
VOC (mg/t-mi)	5	5	15	56	25	1.25
CO (mg/t-mi)	10	5	205	93	220	0.90
NOx (mg/t-mi)	25	15	470	92	515	1.00
PM10 (mg/t-mi)	<1	5	5	29	10	1.00
SOx (mg/t-mi)	10	10	<1	4	20	1.35
FT100
Total energy (Btu/t-mi)	60	570	1100	64	1735	1.35
Petroleum (Btu/t-mi)	5	15	<1	<1	20	<0.05
CO2 (g/t-mi)	5	20	80	76	105	1.05
CH4 (mg/t-mi)	115	65	<1	<1	180	1.80
N2O (mg/t-mi)	<1	<1	<1	64	<1	NA
GHGs (g/t-mi)	10	20	80	73	110	1.05
VOC (mg/t-mi)	5	5	15	53	25	1.25
CO (mg/t-mi)	5	20	150	86	175	0.75
NOx (mg/t-mi)	15	45	410	87	475	0.95
PM10 (mg/t-mi)	<1	15	5	16	15	1.50
SOx (mg/t-mi)	10	20	<1	<1	30	2.00
CNG
Total energy (Btu/t-mi)	95	70	1385	90	1545	1.20
Petroleum (Btu/t-mi)	5	5	<1	<1	10	<0.05
CO2 (g/t-mi)	5	5	80	89	90	0.90
CH4 (mg/t-mi)	290	5	15	5	315	3.15
N2O (mg/t-mi)	<1	<1	<1	43	<1	NA
GHGs (g/t-mi)	15	5	85	82	100	0.95
VOC (mg/t-mi)	5	<1	165	96	170	8.50
CO (mg/t-mi)	10	<1	15	54	25	0.10
NOx (mg/t-mi)	25	5	345	92	375	0.75
PM10 (mg/t-mi)	<1	5	<1	6	5	0.50
SOx (mg/t-mi)	15	5	<1	2	20	1.35
LNG
Total energy (Btu/t-mi)	75	140	1375	86	1595	1.25
Petroleum (Btu/t-mi)	5	10	<1	<1	15	<0.05
CO2 (g/t-mi)	5	10	80	85	95	0.95
CH4 (mg/t-mi)	145	90	50	17	290	2.90
N2O (mg/t-mi)	<1	<1	<1	66	<1	NA
GHGs (g/t-mi)	10	10	85	80	105	1.00
VOC (mg/t-mi)	5	<1	165	95	170	8.50
CO (mg/t-mi)	10	5	15	50	25	0.10
NOx (mg/t-mi)	20	25	345	88	395	0.80
PM10 (mg/t-mi)	<1	<1	<1	14	<1	NA
SOx (mg/t-mi)	15	5	0	<1	15	1.00
Notes: Values rounded to the nearest 5. Total energy use and emissions may not equal the sum of fuel-cycle stages because of rounding. Tailpipe EFs are compiled from numerous sources and calculated assuming a truck carrying a 20-t load.1,2,12,53,54,56–59,76. NA = not applicable.

Table 2. HDV WTP energy consumption and emissions (reported in Btu/MBtu or g/MBtu of fuel available at fuel station pumps) with ratios of alternative fuel values to ULSD values shown in parentheses

Item	ULSD	BD20	ED10	FT100	CNG	LNG
WTP efficiency ^a	84.2%	65.7%	78.1%	60.4%	88.3%	84.7%
Energy consumption
Total energy (Btu/MBtu)	187,300	522,500 (2.79)	280,200 (1.5)	654,900 (3.5)	132,600 (0.71)	180,700 (0.96)
Petroleum (Btu/MBtu)	75,900	88,500 (1.17)	78,500 (1.03)	19,600 (0.26)	7,800 (0.10)	13,000 (0.17)
Emissions (g/MBtu)
CO2	14,500	2,000 (0.13)	12,300 (0.85)	26,100 (1.81)	8,400 (0.58)	12,000 (0.83)
CH4	104	96 (0.92)	105 (1.01)	188 (1.8)	244 (2.34)	199 (1.9)
N2O	0.2	2.7 (11.04)	2.9 (11.59)	0.2 (0.61)	0.2 (0.68)	0.3 (1.03)
GHGs ^b	17,100	5,200 (0.3)	15,800 (0.92)	30,800 (1.8)	14,500 (0.85)	17,000 (0.99)
VOC	7.6	26.5 (3.47)	11.2 (1.46)	12.5 (1.63)	6.4 (0.83)	6.6 (0.86)
CO	11.9	14.5 (1.22)	14.3 (1.2)	25.3 (2.13)	9.4 (0.79)	11.2 (0.94)
NOx	36.3	42.2 (1.16)	40.6 (1.12)	65.9 (1.81)	23.8 (0.65)	38.0 (1.04)
PM10	5.8	6.6 (1.12)	7.0 (1.19)	14.4 (2.46)	3.0 (0.51)	1.2 (0.2)
SOx	15.6	23.3 (1.49)	17.8 (1.14)	29.9 (1.91)	16.3 (1.04)	13.3 (0.85)
Notes: ^aWTP efficiency is the ratio of the energy output of the final fuel product divided by the sum of this energy output and the energy used to produce it; for example, results for ULSD (84.2%) imply that one could obtain 84.2 units of energy for every 100 units of energy involved in the production and use phases of ULSD. ^bTotal GHG emissions values are calculated in CO2 equivalents by applying a 100-yr GWP factor for each individual GHG type.

Figure 3. TFC percent change vs. ULSD HDV: (a) total energy, (b) petroleum, (c) CO₂, and (d) GHGs.

Table 4. Uncertainty results for two important operational phase variables showing the range of input variable values and the range of TFC energy use, petroleum use, and GHG emissions based on these values

Sensitivity Variable	Low and High Value	Fuel Type	Total Energy Use, Btu/t-mi (Low/High)	Total Petroleum Use, Btu/t-mi (Low/High)	Total GHG Emissions, g/t-mi (Low/High)
Truck payload (t cargo/truck)	Low = 15, high = 25	ULSD	1705/1020	1560/935	140/85
		BD20	2125/1275	1235/740	125/75
		ED10	1940/1165	1545/925	135/80
		FT100	2310/1385	25/15	145/90
		CNG	2060/1235	15/10	135/80
		LNG	2125/1275	20/15	140/85
Truck efficiency (mpg)	Low =−25%, high =+25% (from base value ^a )	ULSD	1700/1020	1560/935	140/85
		BD20	2120/1275	1230/740	125/75
		ED10	1940/1160	1545/925	140/85
		FT100	2310/1385	25/15	145/90
		CNG	2060/1235	15/10	135/80
		LNG	2125/1275	20/15	140/85
Notes: ^aSee Table 1 for base mpg values. All table values rounded to the nearest 5 units.

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