Thermal Conversion of Solid Wastes and Biomass - ACS Publications

48 A Preliminary Analysis of the Potential for Developing Nations to Use Biomass Fuels in Vehicle Engines J. L. JONES and A. K. CHATTERJEE

Downloaded by TUFTS UNIV on June 4, 2018 | https://pubs.acs.org Publication Date: August 29, 1980 | doi: 10.1021/bk-1980-0130.ch048

Chemical Engineering Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025

Researchers at the Brookhaven National Laboratory recently reported that oil-importing developing nations contain more than 40% of the world's population but consume less than 10% of the world's commercial energy (1a). In two-thirds of those countries, petroleum supplies at least 90% of the commercial energy (commercial energy refers to conventional fuel or energy forms of commerce such as petroleum,coal, natural gas, and electric power.) In 1975, o i l imports by a l l of the developing countries combined was about 2.7 million barrels per day. As other speakers at this symposium have described, the use of fuel gas produced by biomass or solid waste gasifiers can reduce the use of petroleum fuels in stationary combustion equipment (oil-fired boilers, diesel engines for electric generators or irrigation pumps). Stationary engines and furnaces, however, are not the only big users of petroleum fuels in lesser developed countries (or LDCs, the term we will employ to describe the 88 poorest nations in the world). As is the case for industrialized nations, lesser developed countries need liquid transportation fuels, and probably will for a long time. Brookhaven reports that most LDCs have increased their dependence on highway transport over the last two decades (1b). Biomass fuels offer a possible source of energy for certain LDCs. Vehicle engines may use biomass by such methods as on-board thermal gasification of solid biomass fuels, or the burning of alcohols produced by either fermentation (ethanol) or by thermal gasification and synthesis (methanol). Vehicle-mounted gasifiers are not new. During World War II, securing fuels for transport, agricultural, irrigation, and stationary combustion engines became an acute problem. The development and adoption of biomass gasifiers using charcoal or wood were directed to the transportation sector. Sweden, Germany, France, and Italy were the first nations to adopt biomass gasifiers for transport and agricultural engines. During 1942, the number of biomass gasifiers used for vehicles rose to 821,604 worldwide (2). During that time, the Italian government decreed that Italy's entire fleet of 0-8412-0565-5/80/47-130-689$05.00/0 © 1980 American Chemical Society Jones and Radding; Thermal Conversion of Solid Wastes and Biomass ACS Symposium Series; American Chemical Society: Washington, DC, 1980.


690

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

68,500 agricultural tractors be fitted with biomass gasifiers by 1947. Similarly, Germany ordered that a l l road and farm tractors of more than 25 horsepower (HP) be fueled with biomass fuel gas. By the end of 1944, Sweden reported having nearly 90,000 operational vehicles powered by biomass fuel gas (3). Sweden's statistics showed a preference for charcoal over wood as a gasifier fuel for private cars, small trucks, and motorcycles. Charcoal's popularity resulted from its ease of handling and storage, the small pressure drop it caused in the gasifier, its good thermal efficiency, and its tendency not to slag. Sweden's wood- or charcoal-fueled engines supplied between 10 and 200 HP. They were primarily for over-the-road vehicles, but farm equipment, fishing vessels, road-paving equipment and stationary engines for driving compressors and electric generators were also powered by the wood or charcoal gasifiers. Potential for using alcohol fuels as a substitute or supplement for liquid transportation fuels is a topic of current interest not only in LDCs but in most areas of the world. The use of sucrose from sugar cane or by-product molasses (containing sucrose and various C6 sugars) has been the subject of discussions at several recent meetings of the United Nations Industrial Development Organization (UNIDO) and the Organization for Economic Cooperation and Development (OECD) (4,5). In this paper, we shall present a cursory analysis of the required capital investment for an LDC to substitute biomass fuels for petroleum. We have chosen to analyze only investment costs because, first, alcohol production options are likely to necessitate the construction of relatively large and complex conversion plants. The plants would require substantial capital investments (perhaps with equipment purchased abroad) and a sophisticated engineering and operational staff. Second, the Brookhaven study suggests that, by the year 2000, LDCs outside OPEC will need to increase their annual investments in energy resources by 50% to meet their commercial energy demands. Third, because only a few countries have substantial access to private international investment, the present lending policies will make it difficult for many countries to develop their energy supplies (1c). Fourth, any estimate of operating costs is of questionable value unless the analysis is based on a specific country or region. Thus, we will not compare operating costs, or any other costs related to modifications of fuel distribution networks or changes in agricultural practices that might allow more harvesting of wood or agricultural residues. For this reason, we will be unable to draw firm conclusions concerning the relative economic desirability of the options. We believe, however, that the results should be instructive to planners who will be faced with evaluating future energy options for LDCs.

Jones and Radding; Thermal Conversion of Solid Wastes and Biomass ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

48.

JONES AND CHATTERJEE

Biomass Fuels for Vehicle Engines

691


Bases f o r the A n a l y s i s For t h i s a n a l y s i s , we have assumed that the goal f o r a s p e c i f i c r e g i o n or country i s to r e p l a c e 1000 b a r r e l s / d a y (42,000 g a l l o n s or 159,000 l i t e r s ) of petroleum f u e l s . The heating value of t h i s amount of petroleum f u e l i s ^ 5 . 7 χ 10^ Btu/ day (~· 6 χ 10^-2 j o u l e / d a y ) . The import value of 1000 b a r r e l s per day of petroleum f u e l s i s probably c l o s e to $25,000/day or $9 m i l l i o n / y e a r (assuming a crude o i l p r i c e of ^ $20/barrel on the world market). The types of f u e l that w i l l be considered f o r use i n v e h i c l e mounted g a s i f i e r s i n c l u d e wood chips (^30 weight percent H2O) and d e n s i f i e d f u e l p e l l e t s (^10 weight percent H 2 O ) produced from a g r i c u l t u r a l residues. Two approaches may be used to r e p l a c e petroleum f u e l s with alcohol fuels. The f i r s t i s to blend the a l c o h o l with the petroleum f u e l i n mixtures that c o n t a i n 5 to 20 volume percent alcohol. Blending a l c o h o l s with petroleum f u e l s at such l e v e l s may allow operation of unmodified v e h i c l e s with l i t t l e n o t i c e a b l e change i n the volumetric consumption of f u e l per u n i t of d i s t a n c e traveled. (The question of whether or not the volumetric f u e l consumption changes f o r a l c o h o l blends i s a t o p i c of current research and debate.) Ethanol has a volumetric heat content about two-thirds that of a petroleum f u e l . Methanol, whose weight percent of chemically bound oxygen i s higher than e t h a n o l s , has a volumetric heat con tent about h a l f that of a petroleum f u e l . I f 100% a l c o h o l f u e l s were to r e p l a c e petroleum f u e l s , then the volume of f u e l r e q u i r e d per u n i t of d i s t a n c e t r a v e l e d could increase by as much as 50 to 100% depending on the s p e c i f i c a l c o h o l used and the engine design. For t h i s a n a l y s i s , we w i l l assume that the a l c o h o l f u e l i s mixed with petroleum f u e l s i n a l c o h o l mixtures of 10 to 20 volume percent and that the a l c o h o l f u e l i s s u b s t i t u t e d on an equal-volume b a s i s with petroleum. Therefore, the average a l c o h o l production r a t e s w i l l be 1

Volume/year

Volume/day 1,000 b a r r e l s 42,000 g a l l o n s 159,000 l i t e r s

365,000 b a r r e l s 15.3 m i l l i o n g a l l o n s 58 m i l l i o n l i t e r s

A l c o h o l Fuels Production Ethanol Production from Biomass Feedstock Options. Ethanol may be produced v i a fermentation (with yeast) of 6-carbon or 12-carbon sugars from a number of carbohydrate sources i n c l u d i n g sugar crops, s t a r c h crops, or l i g n o c e l l u l o s i c materials.


692

THERMAL CONVERSION OF

SOLID WASTES AND

BIOMASS


With l i g n o c e l l u l o s i c m a t e r i a l s , such as wood or crop residues (wheat straw, r i c e straw, corn s t o v e r ) , the m a t e r i a l must f i r s t undergo extensive treatment with mineral a c i d s or enzymes to hydrolyze (or s a c c h a r i f y ) the m a t e r i a l to s o l u b l e sugars f o r fermentation. Such procedures have proved h i g h l y expensive; only the USSR c u r r e n t l y has operating commercial p l a n t s that produce sugars from wood by a c i d h y d r o l y s i s techniques. We do not consider such h y d r o l y s i s techniques to be competitive at t h i s time with other conversion methods f o r using l i g n o c e l l u l o s i c m a t e r i a l s i n most regions of the world. Starches present i n grains or r o o t crops are r e a d i l y converted to sugars f o r fermentation to ethanol. With the shortages of food i n developing nations, grains would probably not be used for fuel. Therefore, we w i l l consider only sugar crops and molasses to be a v a i l a b l e f o r ethanol production. In the i n i t i a l part of the a n a l y s i s , we w i l l i d e n t i f y the c o u n t r i e s where suf f i c i e n t sugar i s exported or molasses produced to allow production of ethanol to r e p l a c e 1000 b a r r e l s of petroleum f u e l s . Many developing nations s u s t a i n s u f f i c i e n t sugar production l e v e l s to meet t h e i r own needs and s t i l l export l a r g e tonnages. Table I summarizes the world production and consumption of sucrose, by r e g i o n , f o r 1977, a year i n which production s i g n i f i c a n t l y exceeded consumption. The use of cane sugar j u i c e f o r f u e l pro duction may solve a p o s s i b l e f u t u r e problem r e l a t e d to a decreasing demand f o r sucrose as c e r t a i n i n d u s t r i a l i z e d nations that import sucrose (such as the United States) i n c r e a s e t h e i r production of h i g h - f r u c t o s e corn syrup to r e p l a c e sucrose i n some a p p l i c a t i o n s . In the developing regions of the world, almost a l l of the sucrose production i s from sugar cane. Production f a r exceeds con sumption i n C e n t r a l and South America and i s s l i g h t l y higher than demand i n A f r i c a . Table II l i s t s the 11 major exporters of sucrose that account f o r ~ 75% of the t o t a l exports of world pro ducers. On the b a s i s of the f o l l o w i n g assumed stoichiometry, ^1.63 metric tons of sucrose i s s u f f i c i e n t to produce 1000 l i t e r s of 100% ethanol. 5 C

H

12 22°11 (sucrose)

10 C.H 0. b lz b

f e a s

10

/ 1710

ν kg sucroseW

^828

kg EtOH

r

+

5 H

2° *

1 0 C

H

6 12°6

£ ^ 1 8 C H,0 + 18C0 + 6 (CH 0) 2 6 2 I (ethanol) represents new c e l l s and other products o

/

796 kg EtOH

o

o

. , .1.64 \ / l metric ton\

/\1000 l i t e r s EtOH/\

1000

kg

/

1000

metric tons sucrose l i t e r s EtOH


48.

JONES AND CHATTERJEE TABLE I

1977 WORLD PRODUCTION AND CONSUMPTION OF SUCROSE Production Consumption ( 1 0 M e t r i c Tons/Yr) (% Cane Sugart ( 1 0 M e t r i c Tons/Yr)" b

Region Europe North America C e n t r a l American South American Asia Africa ^ Oceania


693


b

30.48 4.74 13.59 13.72 18.46 6.07 4.76

2 31 100 89+ 88+ 95+ 100

31.74 11.29 4.49 9.07 20.98 5.69 1.05

91.83

61

84.31

Sucrose i s produced from sugar beets or sugar cane. Includes Hawaii, F i j i Source:

and A u s t r a l i a .

Reference _6 TABLE I I SELECTED MAJOR EXPORTERS OF SUCROSE

Country

1977 Exports (metric tons)

Cuba Dominican Republic

6,238,162 1,116,587

Argentina Brazil Peru

958,310 2,486,587 411,832

Taiwan Philippines Thailand

644,000 2,574,825 1,674,540

Mauritius South A f r i c a

673,995 1,383,867

Australia

2,965,249

Source:

Reference 6

TABLE I I I LESSER-DEVELOPED COUNTRIES WITH SUCROSE PRODUCTION LEVELS OF > 600,000 METRIC TON/YEAR (1977 Data) Cuba Mexico Brazil China Peru Iran Source:

India Taiwan Argentina Indonesia Pakistan Egypt

Dominican Repbulic Philippines Thailand Colombia Mauritius

Reference 6.



694

THERMAL CONVERSION OF

SOLID WASTES AND

BIOMASS

To s u b s t i t u t e ethanol f o r 365,000 b a r r e l s / y e a r (85 m i l l i o n l i t e r s ) petroleum f u e l s would r e q u i r e ~ 9 5 , 0 0 0 metric tons of sucrose annually. The t o t a l exports of sucrose from LDCs (~ 18 χ 1θ6 metric tons/year) could be converted to roughly 11 b i l l i o n l i t e r s of ethanol, which i s equivalent on a volumetric b a s i s to ^0.2 m i l l i o n b a r r e l s / d a y of ethanol or 7% of the t o t a l volume of petroleum imported by those countries i n 1975. I f sucrose were to be used as a feedstock, the sugar j u i c e at 10 to 12 weight percent sugar would go d i r e c t l y to fermentation instead of being used to produce raw sucrose c r y s t a l s plus molasses. Even though sucrose cannot now be counted on to provide the major p o r t i o n of l i q u i d f u e l s f o r LDCs,the p o t e n t i a l e x i s t s i n some developing nations f o r producing s i g n i f i c a n t q u a n t i t i e s . In a d d i t i o n to the nine developing nations l i s t e d i n Table II, 16 other c o u n t r i e s now export enough sucrose to produce 1000 b a r r e l s / day of ethanol using the sugar now exported. They are: E l Salvador, Guatemala, Jamaica, T r i n i d a d and Tobago, Guyana, I n d i a , Mozambique, Swaziland and F i j i , Barbados, Nicaragua, Panama, and B o l i v i a . Instead of producing ethanol from cane sugar j u i c e , as mentioned p r e v i o u s l y , countries could continue to export sucrose and the molasses could be used as the feedstock f o r ethanol production. Molasses, an., a l t e r n a t i v e to sucrose, i s a v i s c o u s l i q u i d by-product of raw sucrose production processes. I t s com p o s i t i o n v a r i e s , but, at the time that i t comes from the c e n t r i fuges, i t contains 77 to 84 weight percent t o t a l s o l i d s . The sucrose l e v e l v a r i e s from 25 to 40 weight percent and the C6 sugars from 35 to 12 weight percent, with the sum of the two ( t o t a l sugars) 50 weight percent or higher. Worldwide, the tonnage of molasses produced i s roughly equivalent to about onet h i r d the tonnage of raw sucrose produced. Therefore, about 30 to 31 m i l l i o n metric tons of molasses were produced i n 1977 (see Table I f o r sucrose production d a t a ) . Only c o u n t r i e s that have t o t a l sucrose production l e v e l s of * 600,000 metric tons would have enough molasses a v a i l a b l e to provide the feedstock f o r the ethanol production c a p a c i t y being considered here. The developing nations that have l a r g e sucrose production l e v e l s , aria*" thus l a r g e molasses production l e v e l s , are l i s t e d i n Table I I I . R e l a t i v e Value of Raw Sucrose, Molasses, and Petroleum F u e l s . If developing nations choose to convert sugar and molasses i n t o f u e l s , they w i l l forego income from exports, but they w i l l save money on petroleum imports. Figure 1 shows the r e l a t i o n s h i p s between import c o s t s , export v a l u e s , and product p r i c e s f o r the three commodities. We have assumed, i n the case of using sucrose o r i g i n a l l y to be exported, that the process i s a l t e r e d by e l i m i n a t i n g the steps of c o n c e n t r a t i o n and c r y s t a l l i z a t i o n . Therefore, no molasses would be produced and about 18% more sugar would be


48.


Biomass Fuels for

Vehicle Engines

695

M O L A S S E S PRICE ( $ / M e t r i c T o n ) 32

64

96

128

I

I

I

I

160

I

(A)


SUCROSE PRICE (C/lb)

PRICE OF P E T R O L E U M F U E L P R O D U C T ($/Barrel)

Figure 1. Values of imports and exports as a function of the prices of raw sucrose, molasses, and petroleum fuels (basis: equal volume substitution of 1000 barrels EtOH/'day for 1000 barrels petroleum fuels/day). Note: (+) molasses ~ 80 wt % solids, 50 to 55 wt % C and C sugars; (*) value of molasses based on total sugar content at 2/3 the value of raw sucrose. 6

12


696


contained i n the sugar s o l u t i o n than would be a v a i l a b l e f o r export as c r y s t a l l i n e sucrose. Two cases are i l l u s t r a t e d i n F i g u r e 1; one i s of the use of sugar cane j u i c e f o r fermentation and the other i s of the use of molasses a l o n e . With the world p r i c e of sugar at about 8ç/lb (18c/kg), and the world p r i c e of molasses above $60/metric ton, the p r i c e of petroleum f u e l s must exceed $50/barrel before the value of imports and exports would be i n balance. Average p r i c e s f o r sugar have f l u c t u a t e d g r e a t l y during t h i s decade, as Table IV shows.


TABLE IV AVERAGE SUCROSE PRICES ON LONDON AND NEW YORK MARKETS (C/Ib)

New York London

1971

1972

1973

1974

1975

1976

1977

4.5 4.5

7.4 7.3

9.6 9.6

29.9 30.1

20.4 20.9

11.5 11.6

8.2 8.2

Sugar p r i c e increases have been f o r e c a s t by U.S. Department of A g r i c u l t u r e studies completed i n 1977 and 1978 (_7,8). For the very l a r g e sugar exporters, worldwide demand may not keep pace with the a b i l i t y to expand production so that fermentat i o n to ethanol may provide them with a means to reduce petroleum imports and to keep sugar o f f the market, thus keeping world sugar p r i c e s high. But, even i n t h i s case, the use of ethanol f o r a f u e l may not be the best economic use f o r the a l c o h o l . Use of ethanol as a chemical feedstock may a l s o be economically a t t r a c t i v e . This t o p i c , however, i s beyond the scope of the current analysis. Investment Requirements f o r Ethanol Fermentation. The a c t u a l investment requirements f o r a t o t a l fermentation c a p a c i t y of 365,000 b a r r e l s / y e a r (- 15.3 m i l l i o n g a l l o n s or - 58 m i l l i o n l i t e r s of ethanol) w i l l vary, depending on many f a c t o r s , such as 4

Number of p l a n t s r e q u i r e d to reach c a p a c i t y l e v e l specified.

•

Extent that e x i s t i n g u t i l i t i e s and s e r v i c e s from adjacent sugar m i l l s are used.

•

Average days of p l a n t operation per year ( d a i l y c a p a c i t y i n s t a l l e d to meet annual production l e v e l ) .

•

Process design (batch fermentation time, l e v e l of automation or instrumentation).

•

S p e c i f i c country and s i t e s where p l a n t s are to be constructed.


48.

JONES A N D C H A T T E R J E E


697

If we assume that the fermentation p l a n t s w i l l operate 330 days/year, r e g a r d l e s s of the days of operation of the sugar m i l l s , the investment cost ranges would be roughly as f o l l o w s :


Feedstock

Factors Considered

Range of Estimates Investment Costs: M i l l i o n U.S. D o l l a r s (1979)

Sugar cane j u i c e (10 to 12 wt% sucrose)

No. of p l a n t s : 1 to 4. U t i l i t i e s and general s e r v i c e s : provided by adjacent sugar m i l l ; i n s t a l l e d at fermentation plant

14 to 20

Molasses

No. of p l a n t s : 4 to 6. U t i l i t i e s and general s e r v i c e s : provided by adjacent sugar m i l l ;

20

These estimated investment costs were developed by using data from references 9_ and 10_ and a d j u s t i n g the costs on the b a s i s of current values of c o n s t r u c t i o n cost i n d i c e s and the s p e c i f i c p l a n t c a p a c i t i e s considered. The range of estimated investment costs are equivalent to $0.90 to $1.50/gallon of annual capacity ($0.24 to $ 0 . 4 0 / l i t e r of annual c a p a c i t y ) . The average investment cost f o r more than 200 d i s t i l l e r i e s i n B r a z i l (of an average capacity of 39 m i l l i o n l i t e r s EtOH/year) with roughly a 50/50 s p l i t between those using sugar cane j u i c e and those using molasses i s > $ l V g a l ( o r > $ 0 . 2 6 / l i t e r ) 0-1). Methanol Production from Biomass Feedstock Options. Numerous l i g n o c e l l u l o s i c m a t e r i a l s could be used f o r the production of methanol. The conversion technology e n t a i l s thermal g a s i f i c a t i o n to produce a synthesis gas stream (CO and H2) followed by synthesis to methanol. A g r i c u l t u r a l residues could be used a f t e r chopping and perhaps d e n s i f i c a t i o n into p e l l e t s . The amount of processing r e q u i r e d before g a s i f i c a t i o n w i l l depend on the type of g a s i f i e r chosen. The most s u i t a b l e feedstock i s probably wood, because i t w i l l g e n e r a l l y be the mater i a l a v a i l a b l e at the lowest cost i n the q u a n t i t i e s r e q u i r e d . To produce an amount of methanol equivalent on a volumetric b a s i s to 1000 b a r r e l s / d a y (365,000 b a r r e l s / y e a r ) of petroleum f u e l would r e q u i r e the processing of ~ 500 metric tons/day of wet wood (at 50 weight percent moisture) f o r 330 days/year. This estimate i s based on data presented by Kohan f o r a wood-to-methanol plant (12).



698

THERMAL CONVERSION

OF SOLID WASTES AND

BIOMASS

Wood A v a i l a b i l i t y . Table V summarizes data f o r worldwide wood production i n 1974, plus projected production l e v e l s f o r 1985 and 2000. Note that i n 1974, 47% of the estimated world wood product i o n was f o r f u e l ; 75% of that use was i n developing nations. In 1974, 82% of the roundwood production i n developing nations went for f u e l use. I t has been estimated that the use of wood f o r f u e l w i l l increase by 10% worldwide by 2000, while the t o t a l production of wood w i l l increase by 50% (13). The use of wood f o r f u e l by developing nations has been estimated to increase by 43%, or by 374 m i l l i o n cubic meters/year. In terms of the a c t u a l percent increase i n production, however, pulpwood production f o r LDCs has been estimated to increase the most, 15-fold. These data on pulpwood production i l l u s t r a t e an important point concerning wood use. As c o u n t r i e s develop, wood i s v i t a l l y needed f o r the cons t r u c t i o n of commercial b u i l d i n g s and residences, and f o r paper production. Therefore, even i f the f u e l demand met by wood remains at a constant l e v e l , e i t h e r the t o t a l harvest must increase to s a t i s f y other demands f o r wood or the e f f i c i e n c y of wood u t i l i z a t i o n f o r f u e l must increase so as to r e q u i r e l e s s wood f o r f u e l purposes. In c e r t a i n developing areas of the world, i n c r e a s i n g wood production or even maintaining current production l e v e l s may be d i f f i c u l t . Wood f o r f u e l i s now reported to be scarce i n l a r g e regions of Southern A s i a , A f r i c a n countries bordering the Sahara from Senegal to E t h i o p i a , the Andean c o u n t r i e s , C e n t r a l America, and the Caribbean. D e f o r e s t a t i o n i s already viewed as a s e r i o u s problem i n numerous areas, and r e f o r e s t a t i o n must be s t a r t e d before l a r g e increases i n wood production can be achieved ( I d ) . TABLE V

WORLDWIDE PRODUCTION OF WOOD PRODUCTS

1974 Fuelwood and charcoal I n d u s t r i a l roundwood Sawlogs and veneer logs Pulpwood Other products T o t a l Roundwood

Figures i n parentheses Source:

M i l l i o n Cubic Meters 1985 2000

1170 (860)*

1200 (1014)

799 (136) 340 (15) 202 (40)

983 (200) 669 (96) 208 (51)

1191 (272) 1111 (222) 206 (62)

2511 (1051)

3060 (1361)

3800 (1792)

( ) are f o r developing

1292 (1236)

nations.

Adapted from data i n reference 13.

In view of current f o r e s t resources, i t appears South America o f f e r s the g r e a t e s t opportunity f o r wood use as f u e l . Brazil, for example, i s c u r r e n t l y planning a l a r g e methanol production program based on wood as a feedstock to complement present ethanol


48.



699


production operations that use sugar cane j u i c e or molasses as the main carbohydrate source (14) . In some, other developing c o u n t r i e s , however, i n A f r i c a and Southeast A s i a , the p o t e n t i a l does e x i s t f o r increased long-term use of f o r e s t resources f o r f u e l . But, because of the many v a r i e t i e s of wood produced and the d i f f e r e n c e s i n v a l u e as a f u n c t i o n of wood grade and end use, a d i s c u s s i o n of wood v a l u e i s beyond the scope of t h i s e f f o r t . Investment Requirements f o r Methanol Production from Wood. According to investment cost estimates prepared by Kohan, a p l a n t that would operate 330 days/year and produce 48,000 gallons/day of methanol (182,000 l i t e r s / d a y ) would cost roughly $50 m i l l i o n (12). This investment i s e q u i v a l e n t to $2.50/gallon of annual c a p a c i t y (or $ 0 . 6 6 / l i t e r of annual c a p a c i t y ) . Because s i g n i f i c a n t economies of s c a l e are a c h i e v a b l e i n methanol production, a l a r g e p l a n t i s p r e f e r a b l e to minimize the investment requirements per u n i t of c a p a c i t y . S i n g l e methanol plant c a p a c i t i e s f o r B r a z i l have been proposed with s i g n i f i c a n t l y more than 10 times t h i s c a p a c i t y , and investment costs per u n i t of annual c a p a c i t y have been estimated to be l e s s than $1.25/gallon (14). Vehicle-Mounted

Gasifiers

Feedstock Options In t h i s a n a l y s i s , only a i r - d r i e d wood chips or b i l l e t s , and p e l l e t i z e d a g r i c u l t u r a l r e s i d u e s w i l l be considered. The moisture content of these f u e l s i s assumed to be ^ 20 weight percent. Charc o a l b r i q u e t s a r e a l s o a h i g h l y d e s i r a b l e f u e l , but t h e i r prod u c t i o n r e q u i r e s s i g n i f i c a n t c a p i t a l investment. The use of c h a r c o a l , however, warrants c o n s i d e r a t i o n i n f u t u r e s t u d i e s . (See r e f e r e n c e s _3 and 15 f o r d e t a i l e d d i s c u s s i o n s of biomass f u e l use i n v e h i c l e engines.) Investment

Requirements

The investment requirements f o r r e p l a c i n g 1000 b a r r e l s / d a y of petroleum f u e l by burning a low-heating-value gas produced using v e h i c l e mounted g a s i f i e r s have been estimated based on the c a l c u l a t i o n s and assumptions described i n Table VI. Retrofitting of l a r g e s h o r t - h a u l trucks or buses i n r u r a l areas i s the b a s i s f o r the estimate of an investment cost of from $2 to 4 m i l l i o n . R e t r o f i t t i n g 2000 smaller v e h i c l e s (also operating i n r u r a l areas) at a cost of ^ $2000 each might be a more p r a c t i c a l i n i t i a l g o a l and might be achieved f o r e s s e n t i a l l y the same cost. If f i v e p l a n t s were r e q u i r e d f o r the p r o d u c t i o n of d e n s i f i e d f u e l p e l l e t s from a g r i c u l t u r a l r e s i d u e s , the investment costs f o r a t o t a l c a p a c i t y of 580 m e t r i c tons/day would probably exceed $10 m i l l i o n . Therefore, the investment costs a s s o c i a t e d with the option of using vehicle-mounted g a s i f i e r s may be about $15 m i l l i o n .



1 2

Γ Λ Λ Λ Λ

-ιΤ_

3.65

kg s o l i d f u e l

, Ο Λ

-,

ι.j

£

ι / b

11

\

are used.

The average cost to r e t r o f i t l a r g e v e h i c l e i s estimated to range from $5,000 to $10,000; Therefore, r e t r o f i t t i n g 400 v e h i c l e s would cost from $2 to $4 m i l l i o n .

To r e p l a c e 1000 b a r r e l s of petroleum f u e l w i l l r e q u i r e r e t r o f i t t i n g 400 l a r g e v e h i c l e s (580,000 kg s o l i d fuel/day)/(1425 kg/vehicle/day) = 400 v e h i c l e s .

For 1 hour of o p e r a t i o n with wood, the g a s i f i e r volume must be ~ (285 kg/hr)(/300 kg/m^) =1

The volume could be 50% t h i s amount i f d e n s i f i e d f u e l p e l l e t s

m^

cubic meter (168 cubic meter)

kg/vehicle/day

(300 kg/cubic meter)] = 4.75

f o r 5 hours of operation/day i s 1425

The volume of t h i s f u e l i s at most [1425 kg/

The s o l i d f u e l requirement

kg/hr.

the s o l i d f u e l requirement i s

(300 HP χ 5 hrs) (0.95 kg s o l i d fuel/HP-hr) = 285

For a 300-HP engine operated 5 hours/day,

ι

τ~Γ> ΓΓ~Η—Τ TTT % -i . r j - 7 — τ (or ~ 30 l b s s o l i d f u e l / g a l l o n ) . 159,000 l i t e r s of l i q u i d f u e l l i t e r of l i q u i d f u e l C a l c u l a t i o n of s p e c i f i c f u e l consumption i s based on an engine e f f i c i e n c y of 27% and i s equal to 0.95 kg of s o l i d fuel/HP-hr. =

j o u l e s / d a y / (14.7 χ 1θ6 joules/kg) (0.7)] =580,000 kg/day

580,000 kg s o l i d f u e l

[6 χ 1 0

A thermal e f f i c i e n c y of 70% i n conversion of s o l i d f u e l to a low heating v a l u e gas i s assumed to c a l c u l a t e the s o l i d f u e l requirement.

Wood b i l l e t s or p e l l e t i z e d f u e l s with ^ 20 weight percent moisture are to be used i n downdraft g a s i f i e r s ; the average heating v a l u e of the f u e l i s 6337 Btu/lb (or 14.7 χ 10^ j o u l e s / k g ) .

engines are considered f o r r e t r o f i t t i n g .

BASES AND ASSUMPTIONS FOR THE ANALYSIS OF THE VEHICLE MOUNTED GASIFIER OPTIONS (Replacement of 1000 Barrels/Day of Petroleum Fuels or ~ 6 χ Ι Ο ^ Joules/Day)

Large short h a u l trucks and bases with d i e s e l

TABLE VI


48.



701

Summary and D i s c u s s i o n of F i n d i n g s Investment costs to allow replacement of biomass f u e l s f o r petroleum f u e l s used i n t r a n s p o r t a t i o n appear to be s i g n i f i c a n t for a l l o p t i o n s . To r e p l a c e 1000 b a r r e l s / d a y of petroleum f u e l s w i l l r e q u i r e c a p i t a l investments f o r conversion f a c i l i t i e s as follows :


Option Ethanol p r o d u c t i o n From sugar cane j u i c e From molasses alone Methanol production Vehicle-mounted G a s i f i e r s R e t r o f i t t i n g alone Retrofitting + densified f u e l s production

Estimated Investment ( M i l l i o n s of 1979 U.S. D o l l a r s )

14-20 20 40

£ 4 - 15

For both the cases of methanol production and the use of v e h i c l e mounted g a s i f i e r s , a d d i t i o n a l investments w i l l be a s s o c i a t e d with f a c i l i t i e s and equipment f o r h a r v e s t i n g and t r a n s p o r t of the b i o mass to the conversion s i t e s . In the case of ethanol p r o d u c t i o n from c u r r e n t l y produced sugar cane j u i c e or molasses, the convers i o n f a c i l i t i e s would be constructed adjacent to sugar m i l l s that already are r e c e i v i n g the biomass raw m a t e r i a l . Thus, a d d i t i o n a l investments f o r h a r v e s t i n g and transport equipment would not be required. The use of vehicle-mounted g a s i f i e r s would probably present more l o g i s t i c a l problems (e.g., the need f o r frequent r e f u e l i n g ) than would the use of a l c o h o l f u e l blends. The environmental consequences of u s i n g vehicle-mounted g a s i f i e r s could a l s o be a problem, as could operating r e l i a b i l i t y and engine performance (engine d e r a t i n g and response to l o a d ) . The use of v e h i c l e mounted g a s i f i e r s , however, may represent a simple t e c h n o l o g i c a l o p t i o n that o f f e r s employment i n r u r a l areas and s i g n i f i c a n t savings i n imported f u e l s f o r t r a n s p o r t a t i o n . The use of sugar cane j u i c e or molasses to produce an a l c o h o l f u e l may be d i f f i c u l t to j u s t i f y economically i n c o u n t r i e s where a l l of the excess raw sucrose production (and molasses) can be exported at competitive world p r i c e s . Although much enthusiasm c u r r e n t l y e x i s t s f o r producing ethanol f u e l s from l o c a l sugar crops i n developing n a t i o n s , the r e s u l t s of t h i s very cursory a n a l y s i s i n d i c a t e to us that a t l e a s t one other o p t i o n could supplement petroleum f u e l s used i n t r a n s p o r t a t i o n with biomass f u e l s a t comparable or lower c a p i t a l investments. This o p t i o n i s the use of vehicle-mounted g a s i f i e r s .


702


Conclusions and Recommendations


On the basis of this cursory analysis, vehicle-mounted biomass gasifiers as well as alcohol fuels appear to us to represent possible means to reduce petroleum fuel use in developing nations. Biomass availability for use as a fuel, however, could restrict the use of the option to only a few LDCs. We recommend that, in the future, transportation development plans and energy studies for LDCs include consideration of vehiclemounted gasifiers (especially in rural areas), along with the other options being evaluated. The potential problems with the use of such gasifiers that we have identified in this paper should also be carefully analyzed. LITERATURE CITED 1.

Palmedo, P. F., et a l . , "Energy, Needs, Uses and Resources in Developing Countries," National Center for Analysis of Energy Systems, Brookhaven National Laboratory, (a) p. XV, (b) p. 95 (c) p. XIX (d) pp 52 to 55, March 1978.

2.

Egloft, G., et a l . , "Motor Vehicles Propelled by Producer Gas" The Petroleum Engineer, 115, December 1943 (pp. 65-73).

3.

"Generator Gas—The Swedish Experience from 1935-1945", report translated from Swedish to English by the Solar Energy Research Institute, Golden, Colorado, SERI Publication No. SP-33-140, January 1979, published in Swedish, Stockholm, 1950.

4.

O'Sullivan, D. Α., "UN Workshop Urges Wider Use of Ethanol," Chemical and Engineering News, April 23, 1979.

5.

Molasses and Industrial Alcohol," Proceedings of the Meeting of Experts Organized by the Development Center of the Organisation for Economic Co-operation and Development, Paris, 1976, published by the OECD, Paris, France, 1978.

6.

International Sugar Organization, "Sugar Year Book 1977"; The Whitefriars Press Ltd: London, England, July 1978.

7.

"Report on World Sugar Supply and Demand, 1980 and 1985"; Foreign Agricultural Service, United States Department of Agriculture, Washington, D.C., November 1977.

8.

"An Update on World Sugar Supply and Demand, 1980 and 1985"; Foreign Agricultural Service, United States Department of Agriculture, Washington, D.C., May 1978.

9.

Jones, J. L., Fong, W. S., "Mission Analysis for the Federal Fuels from Biomass Program, Volume V: Biochemical Conversion of Biomass to Fuels and Chemicals"; report prepared by SRI International, Menlo Park, California, for the U.S. Department of Energy, December 1978.


48.

10.


11.


Biomoss Fuels for Vehicle Engines703

Lipinsky, E. S., et a l . , "Second Quarterly Report on Fuels from Sugar Crops"; report prepared by Battelle Memorial Institute, Columbus, Ohio for the U.S. Department of Energy, October 1977. Yang, V., and Trindade, S. C., "Brazil's Gasohol Program"; Chemical Engineering Progress, 75, 4, April 1979 (p. 14).

12.

Kohan, S. Μ., Barkhordar, P. Μ., "Mission Analysis for the Federal Fuels from Biomass Program, Volume IV: Thermochemical Conversion of Biomass to Fuels and Chemicals"; report prepared by SRI International, Menlo Park, CA, for the U.S. Department of Energy, January 1979.

13.

Stone, R. N, Saeman, J. F., "World Demand and Supply of Timber Products to the Year 2000"; Forest Products Journal, 1977, 27(10). "Brazil out to Show Methanol Grows on Trees"; Chemical Week, 1979, 124 (11).

14. 15.

Skov, Ν. Α., Papworth, M. L., "The Pegasus Unit". Publishers, Inc., Olympia, Washington, 1974.

RECEIVED November 20,

Pegasus

1979.


Thermal Conversion of Solid Wastes and Biomass - ACS Publications

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