Potential of Eichhornia crassipes for biomass refining

Abstract

Here we explore the utilization of Eichhornia crassipes, commonly known as water hyacinth, as a competitive source of biomass for conversion to fuel. Ecologically, E. crassipes is the most undesirable of a class of noxious and invasive aquatic vegetation. Water hyacinth grows rapidly on the surface of waterways, forming a dense mat which depletes the surrounding environment of essential nutrients. These properties, rarely encountered in other plant systems, are features of an ideal feedstock for renewable biomass. The high characteristic water content limits the range over which the material can be transported; however it also makes E. crassipes a natural substrate for rapid microbial metabolism that can be employed as a potentially effective biological pretreatment technology. We show through a life cycle analysis that water hyacinth is a competitive feedstock with the potential to be produced at a cost of approximately $40 per ton of dry mass.

Appendices

Appendix A

Crop
A	Lake area covered	300 (acres)	Parameter
G	Annual plant growth	100 (tons DM/ha per year)	Parameter	[14, 30]
M T	Plants grown on lake annually	2.20E+08 (kg/year)	$M_{\rm T} =\frac{{\rm AG}\left({907} \right)\left({0.404} \right)}{1-R_{\rm w,in}}$	Eq. 1
r A	Plant areal density	14 (kg/m2)	Parameter	[29]
t yr	Days/year working	310 (days/year)	Parameter
M D	Mass that can be harvested/day	7.09E+05 (kg/day)	$M_{\rm D} =\frac{M_{\rm T}}{T_{\rm yr}}$	Eq. 2
Harvest
w cut	Cut width	3.5 (m)	Parameter
v cut	Cut speed	45 (m/min)	Parameter	[20]
A H	Area harvested hourly	9,450 (m2/h)	$A_{\rm H} =w_{\rm cut} v_{\rm cut}\left({60} \right)$	Eq. 4
T D	Hours harvested/day	8 (h)	Parameter
A DH	Daily harvest per harvester	75,600 (m2/day)	ADH = AHtD	Eq. 5
M H	Mass plants harvested per harvester	1.06E+06 (kg/day)	MH = ADHρA	Eq. 6
N H	Whole number harvesters required	1	$N_{\rm H}=\frac{M_{\rm D}}{M_{\rm H}}$	Eq. 7 a
A D	Total acres per day harvested	18.7 (acres)	$A_{\rm D} =\frac{A_{\rm DH}N_{\rm H}}{4046}$	Eq. 8
f H	Re-growth rate required to maintain	24 (days)	$f_{\rm H} =\frac{A\left({4046} \right)\rho _{\rm A}}{M_{\rm D}}$	Eq. 3
P H	Harvester energy requirements (each)	100 (kW)	Parameter	[20]
Transportation from lake to storage
C M	Connectivity of hyacinth mats	100 (Pa)	Parameter	[29]
v M	Speed of pulling mat in	2 (m/s)	Parameter
r	Plant density	167 (kg/m3)	Parameter	[2]
l M	Estimated length of hyacinth mats	180 (m)	$l_{\rm M} =\frac{C_{\rm M} \left({600} \right)}{v_{\rm m} \rho}$	Eq. 9
M M	Estimated weight of hyacinth mats	8.80E+03 (kg)	MM = lMwcutρA	Eq. 10
N M	Number of mats pulled daily	81 (mats/day)	$N_{\rm M} =\frac{M_{\rm D}}{M_{\rm M}}$	Eq. 11
P RB	Row boat energy requirements	5 (hp)	Parameter
N RB	Number of operators required	3	$N_{\rm RB} = \frac{{N_{\rm M}}}{{t_{\rm D}} \left({4} \right)}$	Eq. 12 a
Storage/decomposition
M D	Mass of plant material entering	7.09E+05 (kg/day)
R W,in	% Water in material	0.95 (mass %)	Parameter	[14]
M W,in	Total mass water in entering material	6.74E+05 (kg/day)	Mw,in = Rw,inMD	Eq. 13
M B,in	Total mass fiber in enetering material	3.55E+04 (kg/day)	$M_{\rm B,in} =\left({1-R_{\rm w,in}} \right)M_{\rm D}$	Eq. 14 b
R W,rem	Total water removal desired	0.97 (mass %)	Parameter	–c
M P,HR	Mass of plant material processed per hour	2.96E+04 (kg/h)	$M_{\rm P,hr} =\frac{M_{\rm D}}{24}$	Eq. 15 d
M W,rem	Mass of desired water removed	2.72E+04 (kg/h)	$M_{\rm w,rem} =\frac{M_{\rm w,in} R_{\rm w,rem}}{24}$	Eq. 16
M T,out	Total mass leaving presses	2.32E+03 (kg/h)	$M_{\rm T,out} =M_{\rm P,hr} -M_{\rm w,rem}$	Eq. 17
M W,out	Mass water remaining in biomass	8.42E+02 (kg/h)	$M_{\rm w,out} =\frac{M_{\rm w,in}}{24}-M_{\rm w,rem}$	Eq. 18
$M_{\rm B, out}$	Mass biomass leaving presses	1.48E+03 (kg/h)	$M_{\rm B,out} =\frac{M_{\rm B,in}}{24}$	Eq. 19
$R_{\rm W, out}$	Percent water leaving presses	36.31% (mass %)	$R_{\rm w,out} =\frac{M_{\rm w,out}}{M_{\rm T,out}}$	Eq. 20
$R_{\rm B, out}$	Percent biomass leaving presses	63.69% (mass %)	$R_{\rm B,out} =\frac{M_{\rm B,out}}{M_{\rm T,out}}$	Eq. 21
N P	# of presses required to achieve %	6	Parameter	–c
P P	Energy used by each press	29.3 (hp)	$P_{\rm P} =\left({18\,\hbox{hp-hr/ton}} \right)\left({\frac{M_{\rm P,hr} }{907}} \right)\left({1-R_{\rm w,in}} \right)$	Eq. 22 e
P PT	Total energy used	175. 9 (hp)	PPT = NPPP	Eq. 23

1. ^aRounded up
2. ^b1 Day is equivalent to 8 h
3. ^cManufacturer specification
4. ^dProcess becomes continuous
5. ^eManufacturer general rule of thumb: 18 hp/ton fiber per h

Appendix B

Capital
C S	Site	$1,000,000	Parameter
C E	Equipment	$192,000	Parameter
C fix	Fixed capital costs	$1,192,000	CS + CE
C W	Working capital	$119,200	0.1C fix	[35]
C T	Total capital costs	$1,311,200	CW + Cfix
Manpower
MH H	Harvesting	8 (Manhours/day)	T D M H
MH T	Transporting	24 (Manhours/day)	T D N RB
MH P	Pressing/digestion	8 (Manhours/day)	Parameter
C wage	Wage + benefits	$13.00 ($/Manhour)	Parameter
C wage,T	Total, per year	$161,200.00 ($/year)	$(MH_{\rm H}+MH_{\rm T}+MH_{\rm P})C_{\rm wage}t_{\rm yr}$
C wage,S	Supervisory labor, per year	$16,120.00 ($/year)	0.1C wage,T	[35]
Maintenance and operation
C fuel,H	Fuel for harvester	$22,320 ($/year)	tyrtD [3 ($/gal)] ([NHPH 1,000 (W/kW) 3600 (s/hr)]/[43E6 (J/kg)]) [264.172 (gal/m3)/737.22 (kg/m3)]
C fuel,RB	Transport power required	$2,498 ($/year)	tyrtD [3 ($/gal)] ([NRBPRB 1000 (W/kW) 3,600 (s/hr)]/[43E6 (J/kg)]) [264.172 (gal/m3)/737.22 (kg/m3)]
C P	Mill press power	$146,473 ($/year)	[N P P P0.746 (kW/hp)] 0.15 ($/kWh) 24 (hr/day)t yr
C MR	Maintenance and repairs	$19,200 ($/year)	0.1C E	[35]
C OS	Operating supplies	$1,920 ($/year)	0.1C MR	[35]
C O	Overhead	$49,130 ($/year)	0.25(C wage,T + C wage,S + C MR)	[35]
C LT	Local taxes	$11,920 ($/year)	0.01C fix	[35]
C I	Insurance	$23,840 ($/year)	0.02C fix	[35]
C Admin	Administrative costs	$12,283 ($/year)	0.25C O	[35]
C MO	Total maintenance and operation costs	$466,903 ($/year)	$C_{\rm wage,T}+C_{\rm wage,S}+C_{\rm fuel,H}+C_{\rm fuel,RB}+C_{\rm P}+C_{\rm MR}+C_{\rm OS}+C_{\rm O}+C_{\rm LT}+C_{\rm I}+C_{\rm Admin}$
Depreciation
C D	Straight-line depreciation	$59,600 ($/year)	0.05C fix
Credit
C cred	Water hyacinth removal credit	$130 ($/acre)	Parameter	[7, 32]
C total,yr	Total annual cost	$487,503 ($/year)	CMO + CD−(CcredA)
Biomass production
M biomass	Bioimass produced annual	1.21E+04 (ton/year)	[M B,out/907.18 (kg/ton)] [24(hr/day)]t yr
C Final	Price per ton to produce	$40.22 ($/ton)	Ctotal,yr/Mbiomass