Optimal Deployment of Emissions Reduction Technologies for Construction Equipment

Figures & data

Table 1. A brief description of several emissions reduction options

Category	Example	Description
Exhaust gas aftertreatment technologies	DOC	Can reduce PM emissions, but the total NOx emissions remain unchanged for DOC.
	Diesel particulate filter	Physically traps diesel particulates and prevents their release into the atmosphere and can reduce PM emissions.
	Selective catalytic reduction	Capable of reducing NOx, PM, and HC emissions.
	Lean NOx catalysts	Capable of reducing NOx emissions.
Engine technologies	Engine repower and rebuild	Provides NOx and PM reduction benefits.
	Exhaust gas recirculation	Involves recirculation of a portion an engines' exhaust gas into its combustion chambers. Reduces NOx emissions, but increases PM, HC, and CO emissions and causes a fuel economy penalty.
	Crankcase emissions control	Capable of reducing PM emissions.
Fuel technologies	Natural gas	Reduces emissions and provides a potential operating cost savings.
	Biodiesel	Derived from renewable sources such as vegetable oil, animal fat, and cooking oil. Emits more NOx emissions than off-road diesel engines. Compatible for use with high-efficiency catalytic emissions–reduction technology.
	Hydrogen	Has low energy density in the gaseous form. Hence, if less expensive and liquefied hydrogen become readily available, then it becomes practical for use in the nonroad equipment sector.
	Fuel additive	Can reduce engine emissions and/or improve fuel economy. Some manufacturers claim that their products can reduce NOx, HC, PM, and/or CO emissions and can decrease fuel consumption. Some of the products might increase one or more pollutant emissions while reducing other pollutant emissions and increasing fuel efficiency.
	Hydrogen enrichment	HE systems create a better flame front in the engine that helps reduce emissions. Can reduce NOx and CO emissions and decrease fuel consumption.
Notes: DOC = diesel oxidation catalysts.

Figure 1. Flowchart of the overall approach.

Table 2. Nomenclature of the variables used in the model

Variable	Definition
C	Set of NA and NNA counties
n c	Total number of counties
E	Set of different categories of construction equipment
n e	Total categories of construction equipment
n c,e	Total number of equipment of category e in county c
P	Set of different pollutants
n p	Total number of pollutants
T	Set of emissions reduction technologies
n t	Total number of emissions reduction technologies
Em	Emissions from a piece of equipment
C p	Cost of pollutant p
R p,t	Emissions reduction efficiency of technology t for pollutant p
I	Binary variable
AP	Set of analysis periods for each piece of equipment
Fc,e,i.	Fuel consumption of a piece of equipment
C F	Cost of fuel per gallon
FE t	Fuel efficiency of technology t
C t	Cost associated with technology t
Comc,e,i,t	Operation and maintenance costs of technology t for each piece of equipment
ruc,e,i	Remaining usage hours of a piece of equipment
U e,i	Expected usage hours of a piece of equipment
rac,e,i	Remaining age of a piece of equipment
A e,i	Expected age of a piece of equipment

Figure 2. NA and NNA counties in Texas.

Table 3. Data regarding selected emissions reduction technologies

Technology	X	Y	Z
Purchase and installation cost ($)	8400	17100 ^c	18 ^e
Operation cost ($)	–	0.25 ^d	–
Maintenance cost ($)	100 ^a	0.75 ^d	–
Dosage rate (mL)	–	–	4.25 ^f
Fuel efficiency (%)	8 ^b	−1	–
NOx reduction efficiency (%)	36	80	5.8
NOx combined reduction efficiency (%)	41.8	81.16 ^g	–
Notes: ^aPer year; ^bAfter 240 hr of operation; ^cWithin 101–300 hp; ^dPer hour; ^ePer gallon of Z; ^fPer gallon of diesel; ^gOn the basis of consultation with the vendor for Y.

Table 4. Cost of NO_x obtained from different studies

Pollutant	HERS Model30 ($/t)	Delucchi33	Small and Kazimi34 and Levinson36 ($/t) ^a
		Low ($/t)		High ($/t)
NOx	3,625	1,445 (1.59)	21,180 (23.34)	1,210 (1.33)
Notes: Values in parentheses are in $/kg as obtained from the studies. ^aValues obtained by Small and Kazimi as modified by Levinson.

Table 5. Value of W1 and W2 for different cases

	Weights Associated with Benefits for
Cases	NOx Reduction, W1	Fuel Savings, W2
1A and 2A	1	0
1B and 2B	0.7	0.3
1C and 2C	0.5	0.5 (base case)
1D and 2D	0.3	0.7
1E and 2E	0	1

Table 6. Analysis scheme

Approach	Options	Cases
Method 1 (In the first stage deploy X, Y, and Z in NA counties; in second stage, deploy same technologies in NNA counties with remaining budget, if any)	Different combinations of two weighted objectives (i.e., NOx reduction and fuel savings; see Table 5)	1A, 1B, 1C, 1D, and 1E
Method 2 (In the first stage, deploy X, Y, and Z in NA counties and Z in NNA counties; in second stage, deploy X or Y on any given equipment in the NNA counties with remaining budget, if any)		2A, 2B, 2C, 2D, and 2E

Figure 3. Flowcharts of methods 1 and 2.

Table 7a. Comparison of cases for total NO_x reductions

Comparison Type	Cases Compared	Budget Range ($)	Outcome	Range of Total NOx Reduction (t)
Comparison of cases with the base case under method 1	1A vs. 1C	90–120,000; 180,000–300,000; 900,000–1,200,000	1C>1A	0.0038–3.12
		Remaining budgets	1A≥1C	0–2.47
	1B vs. 1C	500–100,000	1B≥1C	0–1.72
		180,000–300,000		0.67–2.35
		600,000–1,500,000		0–0.78
		150,000–170,000	1C>1B	1.3–1.6
		400,000–500,000		0.51–2.48
	1C vs. 1D	500–50,000	1C≥1D	0–3.12
		80,000–110,000		0–3.70
		150,000–180,000		0.2–2.65
		300,000–1,500,000		0.28–5.74
		Remaining budgets	1D>1C	0.12–1.96
	1C vs. 1E	Entire budget range	1C>1E	0.57–51.51
Comparison of cases with the base case under method 2	2A vs. 2C	60,000–70,000	2A>2C	0.01–0.15
		90,000–700,000		0.04–0.98
		900,000–1,200,000		0.08–0.80
	2B vs. 2C	Entire budget range	2B≥2C	0–0.86
	2C vs. 2D	90,000–1,150,000	2C>2D	0.39–18.30
	2C vs. 2E	Entire budget range	2C>2E	0.60–51.51
Comparison of corresponding cases under methods 1 and 2	1A vs. 2A	500–500,000	2A>1A	0.03–2.73
		800,000–1,150,000	1A≥2A	0–0.084
	1B vs. 2B	500–500,000	2B>1B	0.03–3.05
		800,000–1,500,000	1B≥2B	0–0.11
	1C vs. 2C	500–200,000	2C>1C	0.03–3.50
		400,000–1,500,000	1C>2C	0–0.30
	1D vs. 2D	500–600,000	2D>1D	0.03–3.75
		800,000–1,150,000	1D≥2D	0–0.66

Table 7b. Comparison of cases for total combined benefits

Comparison Type	Cases Compared	Budget Range ($)	Outcome	Range of Total Combined Benefit
Comparison of cases with the base case under method 1	1A vs. 1C	130,000–200,000; 400,000–1,200,000	1C≥1A	$0–11,100
		Remaining budgets	1A≥1C	$0–6,800
	1B vs. 1C	110,000–190,000	1C>1B	$320–8,865
		400,000–1,500,000		$30–9,855
		Remaining budgets	1B≥1C	$0–3,740
	1C vs. 1D	500–50,000	1C≥1D	$0–9,770
		80,000–110,000		$0–9,950
		150,000–180,000		$3,260–6,620
		300,000–600,000		$2,750–13,570
		1,100,000–1,500,000		$1,005–3,660
		Remaining budgets	1D>1C	$125–7,910
	1C vs. 1E	Entire budget range	1C>1E	$1,950–152,470
Comparison of cases with the base case under method 2	2A vs. 2C	500–1,000,000	2C≥2A	$0–3,970
		1,140,000–1,500,000		$0–100
		1,100,000–1,130,000	2A>2C	$10–40
	2B vs. 2C	500–1,000,000	2C≥2B	$0–1,480
		1,160,000–1,500,000		$0–100
		1,100,000–1,150,000	2B>2C	$10–170
	2C vs. 2D	90,000–1,150,000	2C>2D	$1,605–55,970
	2C vs. 2E	Entire budget range	2C>2E	$2,040–152,470
Comparison of corresponding cases under methods 1 and 2	1A vs. 2A	500–900,000	2A>1A	$90–8,675
	1B vs. 2B	500–1,000,000	2B>1B	$90–9,110
		1,140,000–1,190,000		$15–110
	1C vs. 2C	500–200,000	2C>1C	$90–9,485
		400,000–1,500,000	1C≥2C	$0–170
	1D vs. 2D	500–900,000	2D>1D	$90–11,330
		1,000,000–1,500,000	1D≥2D	$0–1,300

Figure 4. Total benefits for different budgets in methods 1 and 2 in the first year of deployment.

Figure 5. NO_x reductions and benefits obtained by method 1: (a) total NO_x reductions, and (b) total combined benefits.

Figure 7. Comparison between cases: (a) total NO_x reductions (case 1A vs. case 2A), (b) total combined benefits (case 1A vs. case 2A), (c) total NO_x reductions (case 1B vs. case 2B), (d) total combined benefits (case 1B vs. case 2B), (e) total NO_x reductions (case 1C vs. case 2C). (f) total combined benefits (case 1C vs. case 2C), (g) total NO_x reductions (case 1D vs. case 2D), (h) total combined benefits (case 1D vs. case 2D), and (i) total NO_x reductions and total combined benefits for case 1E and case 2E.

Figure 6. NO_x reductions and benefits obtained by method 2: (a) total NO_x reductions, and (b) total combined benefits.

Figure 8. Identification of Pareto front for methods 1 and 2 (all cases): (a) feasible solution sets and (b) Pareto front.

Table 8. Summary of Pareto front for methods 1 and 2

Budget ($)	Case	Total NOx Reduced (t)	Total NOx Reduced ($)	Total Fuel Savings ($) ^a
1,180,000	1A	67.24	223,824	−4,592
1,200,000	1A	67.71	225,385	−4,595
1,300,000	1A	68.90	229,324	−4,975
1,180,000	1B	67.24	223,824	−4,592
1,200,000	1B	67.71	225,385	−4,595
1,300,000	1B	68.90	229,324	−4,975
1,200,000	1C	67.60	225,037	−4,151
1,300,000	1C	68.90	229,324	−4,975
200,000	1D	34.34	114,576	6,830
300,000	1D	34.33	114,372	7,231
400,000	1D	37.99	126,572	6,451
1,000,000	1D	58.86	196,005	4,736
1,100,000	1D	62.90	209,402	1,768
400,000	1E or 2E	17.39	57,730	14,153
1,180,000	2A	67.24	223,824	−4,592
1,200,000	2A	67.71	225,385	−4,595
1,300,000	2A	68.90	229,324	−4,975
1,190,000	2B	67.44	224,488	−4,422
1,200,000	2B	67.71	225,385	−4,595
1,300,000	2B	68.90	229,324	−4,975
1,190,000	2C	67.21	223,729	−3,788
1,200,000	2C	67.60	225,037	−4,151
1,300,000	2C	68.90	229,324	−4,975
200,000	2D	34.34	114,576	6,830
300,000	2D	38.07	126,990	5,765
1,000,000	2D	58.20	193,801	5,637
1,100,000	2D	62.63	208,534	2,131
1,110,000	2D	63.04	209,874	1,768
1,120,000	2D	63.31	210,771	1,595
1,130,000	2D	63.80	212,422	1,092
1,140,000	2D	64.20	213,730	729
1,160,000	2D	64.47	214,647	683
1,170,000	2D	64.63	215,161	630
1,180,000	2D	64.75	215,570	607
1,190,000	2D	65.45	217,880	−231
1,200,000	2D	66.07	219,931	−985
1,300,000	2D	66.80	222,378	−1,686
Notes: ^aNegative value in this column indicates a fuel penalty.

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