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RALPH OVEREND

oil

National Research Council, Rm 206, Bldg M-50, Montreal Rd., Ottawa, Ontario, Canada K1A 0R6

Canada is a country of over 10 million km2 in extent with a small population of about 23 million. Though possessing natural resources on a large scale; traditional sources of crude o i l are declining, and as with the world as whole a transition is taking place in which alternative fuels are being examined. Already syncrudes are being produced from o i l sands and heavy oils and these sources are predicted to be major sources of liquid fuels by the end of the century. Coal and renewable sources of energy are being studied as to their possible contributions as either substitutes for o i l in non critical applications not requiring those attributes such as high energy density demanded of transportation fuels; or in the production of liquid fuels directly. The R&D effort in renewable energy includes an extensive effort in the area of biomass fuels. After initial assessments of the potential of MSW, agricultural residues and crops and forestry (1) it has been recognised that while a l l three renewable resources will contribute to the near term substitution of liquid fuels in non critical applications, only forests and the recently dead form of biomass - Peat - can contribute liquid fuels on a scale close to that demanded which is to say at the Exajoule level. The Canadian forest covers almost one third of the land mass, while agriculture utilises less than 7 per cent. At least 10 per cent of the land area is underlain with organic terrain variously described as muskeg and peat. Peat which is not renewable in the sense that trees are; is; however a low grade resource with biomass characteristics such as heterogeneity, high moisture content and high combined oxygen content with low ash and sulphur contents. The mature forest has an energy density of around 5 Terajoule per hectare whilst the average peat energy density is around 16 TJ/ha, both of which might be compared to the Athabasca sands or coal which have a real energy densities of over 1000 times i.e. 10 - 50 Petajoules per hectare. Thus forests and peat not only share similar raw material characteristics but both have large and widespread implications with respect to land use and water resources.

0-8412-0565-5/80/ 47-130-317$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.

318

THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

The R&D program i s intended to chart pathways through the matrix of p o s s i b i l i t i e s i l l u s t r a t e d i n f i g u r e I. Obviously the system to be optimised i s the pathway from resource to end use; however as can be seen the conversion technology plays a p i v o t a l r o l e i n determining that optimum. The Role of Conversion Technology

i n Biomass

Peat and f o r e s t resources are i n general f a r from the popul a t i o n that they are r e q u i r e d to serve so that the immediate goal of the conversion process can be seen to be that of p r o v i d i n g a t r a n s p o r t a b l e commodity that maximises the energy t r a n s f e r per unit distance. The conversion technology a l s o serves to match "impedances", i t i s the transformer that moves a wet, bulky, heterogenous, h i g h l y oxegenated substance i n t o the a p p l i c a t i o n s that provide us with the goods and s e r v i c e s we r e q u i r e . Conversion Process E v a l u a t i o n s While the t o p i c of t h i s paper i s Canada's PTGL ( P y r o l y s i s Thermal G a s i f i c a t i o n and L i q u e f a c t i o n ) research program i t i s u s e f u l to review the current status of conversion technologies f o r biomass. The goal i s to d e s c r i b e the c h a r a c t e r i s t i c s of each technology so that e f f i c i e n c i e s , process steps and environmental f a c t o r s are w e l l q u a n t i f i e d and under these circumstances f o r a known cost and nature of feedstock an economic or s o c i a l d e c i s i o n can be taken as to whether or not to implement the technology. With the exception of combustion technology the data base i s f a r from t h i s i d e a l ; p r o s p e c t i v e processes range i n development status from conceptual designs through 10 gram batch process s c a l e to 20 tpd process development or demonstration u n i t s . The cost of the feedstock i s e q u a l l y vague - the f o r e s t industry could i n p r i n c i p l e d i s p l a c e a l l n o n - t r a n s p o r t a t i o n / f o s s i l f u e l needs by using r e l a t i v e l y low cost s e l f - g e n e r a t e d residues i n w e l l e s t a b l i s h e d combustion technologies — thus l a r g e s c a l e use w i l l r e q u i r e harvest or c o l l e c t i o n of the f u e l . F o r e s t residues - tops and branches - are n u m e r i c a l l y adequate though harvesting technology f o r t h i s m a t e r i a l i s almost non e x i s t e n t ; peat f o r dry thermal uses i s expensive (_2) c o s t i n g around $1.3/GJ because of short seasons f o r d r y i n g with s o l a r energy and concomitant storage c o s t s ; yet i n p r i n c i p l e , peat i f useable i n the wet s t a t e could be harvested by mining techniques on a year round basis. To f a c i l i t a t e comparison of d i f f e r e n t technologies using widely d i f f e r e n t p r i c e s of feedstock a simple l i f e c y c l e c o s t i n g method i s developed below f o r use with the conceptual supply curve f o r biomass ( e x c l u s i v e of peat) i l l u s t r a t e d i n f i g u r e I I . The supply curve has been developed mainly from data contained i n reference(l).

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

H

4-»

PQ

w

e

M Ρ QJ H C/ H P C J H U H rJ

Ρ

e

u ω xi Ο

ο

^

Β u

ο CJ

eu PH

CO 1 CO CO CU Ρ CJ rP ο

Ο

Ρ cd

ο

S

PQ PQ

r-H

X

rH

4-1

is 5s

4J CO

326

THERMAL

CONVERSION

OF

SOLID

WASTES

AND

BIOMASS

5

Β / A

Figure 3.

Equation C / A = E/(l + 0.15Ό) - Β / Α · l/ (Ό/1 + 0.15Ό) where η = 20 years, i = 10%, and f 3% v


24.

OVEREND

Canada's Biomass Conversion Technology

Reference p r i c e s f o r the opportunity Oil

Gasoline

327

cost "A" are:

20$/Bbl (U.S.) or 23.50$/Bbl (Cdn) =

3.84$/GJ f o r both O i l and Gas

=

5.49$/GJ

E l e c t r i c i t y 2.5c/kWh = 6.94$/GJ eg nuclear

N.N.

5.0c/kWh

13.89$/GJ

eg f o s s i l f u e l e d

15.0c/kWh

41.67$/GJ

eg remote northern communities.

1 Btu = 1.055 kJ 1 kWh = 3.6 MJ

Technology Assessment

Conclusions

The t a b l e I can be summarised i n t o generic c l a s s e s and using a conversion of 18.6 GJ/tonne f o r wood biomass the data i n t a b l e II can be generated i n which biomass costs t e c h n i c a l r i s k and l i k e l y market share are enumerated. Quick i n s p e c t i o n of t h i s table shows that the "easy" low cost m i l l residues w i l l l i k e l y be consumed w i t h i n the f o r e s t i n d u s t r i e s using w e l l developed combust i o n technology. Conversely l i q u i d f u e l s while having an extremely l a r g e p o t e n t i a l market are constrained to a very low cost requirement f o r t h e i r feedstock which cannot be met by current harvesting technology. The supply curve of f i g u r e 2 i n d i c a t e s that the l i k e l y average cost of the 500 PJ/annum increment beyond the a n t i c i p a t e d f o r e s t i n d u s t r i e s expansion w i l l be around 30$/0dt f o r the supply. These f i g u r e s may appear to be daunting economic goals f o r biomass not to be r e s t r i c t e d to e s s e n t i a l l y c a p t i v e use w i t h i n the present biomass i n d u s t r i e s . An opportunity cost of 3.84 $/GJ coupled to a 40% e f f i c i e n t process c o n s t r a i n s the c a p i t a l cost to 1.5 k$/TJ/annum output c a p a c i t y . Only the d e n s i f i e d biomass option coupled with g a s i f i e r s a t the point of use can meet t h i s cost c r i t e r i o n allowing that there w i l l be prepared f u e l t r a n s p o r t a t i o n c o s t s . I f the l i q u i d f u e l opportunity cost of $5.49 i s used then the c a p i t a l cost f o r the conversion has to be l e s s than 7.9 k$/TJ/annum output c a p a c i t y . Allowing that the usual s c a l i n g law of an exponent to the 0.7 power i s l i k e l y to apply to methanol p l a n t s f o r example then a 4000 tpd p l a n t would be f e a s i b l e . MacKay (_3) has shown that s c a l e increases e f f e c t i v e l y outweigh



U t i l i t y p l a n t s of greater than 50 MW. Very dependent on r e g i o n . Market share l i k e l y to be low. Depends on r e g i o n . Unit s i z e i s l e s s than 250 kW i n Canada. 50 MW market i n northern r e g i o n s . P o t e n t i a l market 1 EJ. End use compatibi l i t y problems f o r MeOH upgrading d i f f i c u l t i e s f o r hydrogenated wood products.

ν - low

moderate

moderate to high

12

160

0-10

Electricity

Remote Community and LDC a p p l i c a t i o n s of G a s i f i e r / D i e s e l

Liquid

Fuels

Gasification

High temperature processes and n a t u r a l gas s u b s t i t u t i o n . Retrofit potential for o i l and gas b o i l e r s .

51

Densified Biomass

moderate

Large steam users i n f o r e s t Ind. about 600 MW f e a s i b l e . (20 PJ)

ν - low

55

Forest I n d u s t r i e s S e l f - S u f f i c i e n c y present 300 P J . 1985 600 PJ

POSSIBLE END USE MARKET & SHARE

ν - low

TECHNICAL RISK

E x t e r n a l to F o r e s t I n d u s t r i e s . Mining, I n d u s t r i a l process steam heating plants e t c . Mainly to d i s p l a c e d i s t i l l a t e fuels.

44-70

70

BIOMASS COST $/ODt

low

Co-Generation i n Forest Ind.

Direct Combustion

TECHNOLOGY

TECHNOLOGY ASSESSMENT SUMMARY

TABLE I I

Κ) oo

24.

OVEREND


329

the incremental h a r v e s t i n g costs of i n c r e a s i n g the supply base so that t h i s option i s not e n t i r e l y out of reach. I t i s worth exam i n i n g not only the economic c o n s t r a i n t s but a l s o some of the chemical and end use c o n s t r a i n t s f o r biomass derived f u e l s . T

Dulong s Formula and the Choice of Biomass Derived F u e l Form Uulong's formula i s used to p r e d i c t the higher heating value of f u e l s c o n t a i n i n g v a r i o u s percentages by weight of carbon, hydrogen and oxygen. Q, = 338.3 C + 1442 (H-0/8) η where

= higher heating value of f u e l i n J/g C

= per cent of carbon

Η

= per cent of hydrogen

0

= per cent of oxygen.

The percentages of C,H,0 are by mass on a dry and ash f r e e b a s i s . I f the t a b l e of higher heating values f o r simple organic compounds i n Perry (4) i s used as the true values then the c a l c u l a t e d values from the above formula f i t a s t r a i g h t l i n e of slope 1.04 with an i n t e r c e p t of - 1502 J/g and a c o r r e l a t i o n c o e f f i c i e n t of 0.99. The r e l a t i o n s h i p i s e v i d e n t l y a good f i t with at most 5 per cent e r r o r i n p r e d i c t i n g the higher heating value of a compound of s p e c i f i e d C,H and 0 composition. The greatest e r r o r i s obtained for carbon monoxide where 4208 J/g i s c a l c u l a t e d when the true value i s 10110 J/g. Since biomass i s e s s e n t i a l l y f r e e of n i t r o g e n and sulphur the three components c o n t r o l the heating value and s a t i s f y the r e l a t i o n s h i p 100 = C + Η + 0. Thus a l l biomass derived compounds can be assigned a unique coordinate on a t r i a n g u l a r g r i d as i s i n d i c a t e d i n f i g u r e 4, on which the Dulong heats of combustion are a l s o i n d i c a t e d . The t r i a n g u l a r coordinates i n c l u d e a l l com p o s i t i o n s unconstrained by chemistry so that heating values f o r compositions c o n t a i n i n g more than 24 per cent hydrogen are not feasible. Inspection however shows that the i d e a l conversion technology f o r biomass w i l l be one that l o s e s oxygen while maxi mising the hydrogen to carbon r a t i o . Figure 5, i s the same f i g u r e as the previous one with the v e c t o r s shown f o r d i f f e r e n t techniques of oxygen removal namely as water, carbon d i o x i d e and carbon monoxide. Ignoring f o r the present the p r e c i s e chemistry by which t h i s i s achieved some general p o i n t s can be made i ) Methanol i s a compound that i s l e s s optimum i n composi t i o n than wood with the s o l e v i r t u e of being a l i q u i d that i s j u s t and so compatible with the g a s o l i n e system, i i ) Water removal w i l l produce a carbonaceous f u e l , i i i ) The most l o g i c a l moiety to remove i s carbon monoxide as the product v e c t o r i s most c l o s e to a saturated hydro carbon f u e l .



330

Figure 4.

Dulong diagram heat of combustion and CHO composition

Figure 5.

Biomass conversion routes


24.

OVEREND

331


The removal of a l l oxygen as carbon monoxide can be summarised as follows on a mole b a s i s .

(CH

)

1.45°0.64 n

n

°'

3 6C H

4

+

n

°-

6 4 C

0

The thermochemistry of the three vectors ranges from thermoneutral for water removal to 2.2 GJ/t endothermic f o r carbon d i o x i d e removal and 4.5 GJ/t endothermic f o r carbon monoxide removal. The heat of combustion of the carbon monoxide i s however 7.66 GJ so that i t could be used e i t h e r as a chemical reagent or as a heat source i n an e n t i r e l y biomass f u e l e d process to produce f u e l s that most c l o s e l y approximate todays p r e f e r r e d hydrocarbon f u e l s . Canadian PTGL R&D Goals P y r o l y s i s , G a s i f i c a t i o n and L i q u e f a c t i o n have high p r i o r i t i e s w i t h i n the Canadian R&D program with minor emphasis on d i r e c t combustion technology. D i r e c t combustion i s an o l d but w e l l e s t a b l i s h e d technology with nevertheless some c h a r a c t e r i s t i c s that s t i l l r e q u i r e development e f f o r t s . The present day systems used to burn bark and hog f u e l use supplementary f u e l s such as f u e l o i l and n a t u r a l gas to minimise emissions and the compensate f o r feedstock moisture v a r i a t i o n s . The net e f f i c i e n c y of burning wet wood with considerable excess a i r r a t i o s i s poor and leaves a l o t to be d e s i r e d . During the eco-excesses of the s i x t i e s t h i s was acceptable because the l a r g e hog b o i l e r s were used as d i s p o s a l u n i t s f o r excess r e s i d u e s . Since that time more r e s i d u e has entered the process as f i b r e and of course the over f i r e f u e l s have become very expensive. Because of the f o r e s t i n d u s t r i e s economic importance and the s i g n i f i c a n t savings of f o s s i l f u e l s that might accrue i t i s l i k e l y that d i r e c t combustion w i l l become a higher p r i o r i t y . Already i n the case of experimental work on f l u i d bed combustors f o r high sulphur coals p r o v i s i o n i s being made to study low grade f u e l s such as wet wood and d r i e d peats. In the Canadian context there need not be a r e s t r i c t i o n on biomass conversion processes to be s e l f - s u f f i c i e n t and therefore be r e q u i r e d to s a c r i f i c e carbon to d r i v e the processes, N a t u r a l gas and hydro/nuclear e l e c t r i c i t y are l i k e l y to be a v a i l a b l e on a large s c a l e through to the e a r l y decades of the next century. One or a l l of the f o l l o w i n g options have been discussed i n the context of biomass conversion and i n the s p e c i f i c case of methane a d d i tions to a l t e r hydrogen to carbon monoxide r a t i o s i n syn gas work i s p r e s e n t l y under way to combine oxygen blown wood g a s i f i c a t i o n with the reforming of n a t u r a l gas, (5). 1


THERMAL

332

CONVERSION OF SOLID WASTES AND BIOMASS

Table of Supplementary Sources f o r Biomass Conversion Supplementary Source

Chemical Effect

E x t e r n a l Heat

E l i m i n a t e s need to s a c r i f i c e carbon

Thermal Power S t a t i o n s eg f l u i d bed c o a l combustion or nuclear e l e c t r i c "Co-generated" thermal energy

Hydrogen

Chemical reagent f o r "CO" removal and hydrogénation

Steam reformed n a t u r a l gas, e l e c t r o l y t i c hydrogen generation from WECS, Hydro or nuclear

Electricity

Very high temperature plasma chemistry and or d i r e c t electrochemical r e d u c t i o n of biomass

WECS, Hydro or nuclear sources

Origin

Such complimentary synthesis routes or "HYBRIDS" can achieve remarkable reductions i n c a p i t a l cost and expensive biomass carbon u t i l i s a t i o n . The methane and wood hybrid to produce methanol from the r e s u l t i n g syn-gas would use 7 2 2 m of n a t u r a l gas and 0 . 4 tonne of biomass to produce 1 tonne of methanol a t a c a p i t a l cost of around 1 0 k$/TJ/annum c a p a c i t y on the 1 0 0 0 tpd product s c a l e . Though part of the feedstock i s then p r i c e d a t the i n t e r n a t i o n a l o i l p r i c e (energy equivalent) a p l a n t s c a l e of 3 0 0 0 tpd operating a t 6 0 per cent e f f i c i e n c y w i l l meet the economic c r i t e r i a of the simple model used i n t h i s paper. Hybrids can be viewed as "bridge" technologies which w i l l smooth the t r a n s i t i o n from d e p l e t a b l e resources to an era i n which renewables and i n e x h a u s t i b l e s such as c o a l and p o s s i b l y nuclear f i s s i o n (breeder) are the dominant resources, ( 6 ) . The Canadian Programme The Canadian R&D program i s described a t the i n d i v i d u a l p r o j e c t l e v e l i n Bioenergy Research and Development Program Review 1 9 7 8 , Ç 7 ) . From the preceeding d i s c u s s i o n i t can be seen that the major goal i s to produce a l i q u i d f u e l or l i q u i d f u e l s u b s t i t u t i o n product. A 1 EJ displacement of f o s s i l f u e l s would be equivalent to a doubling of todays roundwood harvest, ( 8 ) . Feedstock cost r e d u c t i o n i s r e q u i r e d and t h i s i s l i k e l y to be obtained by developing technology appropriate to biomass harvesting rather than the present roundwood systems.


24.

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333

A short term goal of the feedstock conversion programme i s to prove the gasification process step of synthesis gas produc tion from biomass. This i s being developed for both the methane HYBRID and the biomass only case for both oxygen and a i r blown gasifiers. The short term goal to produce synthesis gas as a precursor for methanol acknowledges the possible wide-spread adoption of methanol i n the early nineties as a result of catas trophic shortfalls i n the world petroleum supply. Preparation of non-oxygenated or essentially hydrocarbon fuels i s i n an early stage of development; however, provided that early adoption of methanol does not occur, this route offers f l e x i b i l i t y of choice for what i s after a l l an unknown vehicle power plant configura tion of the 21. The current program i s funded out to 1984 at which time i t i s anticipated that there w i l l be sufficient data available to make a decision on whether or not to have a large bioenergy contribution to the energy diet of the nineties.

REFERENCES 1.

InterGroup Consulting Economists. Resources: F e a s i b i l i t y Study";

"Liquid Fuels from Renewable

Volume C: Forest Studies; Volume D: Agricultural Studies; Volume E: Municipal Waste Studies. Fisheries and Environment Canada:

Ottawa 1978.

2. Montreal Engineering Co L t d , "The Mining of Peat - A Canadian Energy Resource"; Energy Mines and Resources Canada: Ottawa 1978. 3. Chemical Engineering Research Consultants L t d , "The Production of Synthetic Liquid Fuels for Ontario"; Ministry of Energy Ontario: Toronto 1977; Volume 5. 4. Perry, R. H . ; Chilton, C. Η., Eds. "Chemical Engineers Handbook"; McGraw Hill: New York 1963; 5th Edition. 5. InterGroup Consulting Economists, "Liquid Fuels from Renewable Resources: F e a s i b i l i t y Study"; Volume B: Conversion Studies; Fisheries and Environment Canada: Ottawa 1978. 6.

Gander, J.E.; Belaire, F. W. "Energy Futures for Canadians," Report EP 78-1; Energy Mines and Resources: Ottawa 1978.


334 7.


Summers, Β.A. "Bioenergy Research and Development - Program Review," NRCC 17671; National Research Council of Canada: Ottawa 1979.

8. Love, P . ; Overend, R. "Tree Power: An Assessment of the Energy Potential of Forest Biomass i n Canada," Report ER 78-1; Energy Mines and Resources: Ottawa 1978. 9. Levelton, B . H . ; and Associates. "An Evaluation of Wood Waste Energy Conversion Systems," Report to the B r i t i s h Columbia Wood Waste Energy Co-Ordinating Committee: Fisheries and Environment Canada: Ottawa 1978. 10.

Acres Shawinigan Ltd. "Hearst Wood Waste Energy Study: Report," Ministry of Energy Ontario: Toronto 1979.

Summary

11. H.A. Simons (International) Ltd. "Hog-Fuel Co-Generation Study. Quesnel, B r i t i s h Columbia," Report to the B r i t i s h Columbia Wood Waste Energy Co-ordinating Committee: Fisheries and Environment Canada: Ottawa 1978. 12. S.N.C. Tottrup Services Ltd. "Energy and Chemicals from Wood," ENR Report No. 90; Department of Energy and Natural Resources Alberta: Edmonton 1979. 13.

Kohan, S.M.; Barkhordar, P.M. "Mission Analysis for the Federal Fuels from Biomass Program, Volume IV: Thermochemical Conversion of Biomass to Fuels and Chemicals, "Report prepared by SRI International for the US DOE: Washington D.C. 1979.

14. Archibald, W.B.; Gabriel, J . A . "Economics of Co-generation i n "Hardware for Energy Generation i n the Forest Products Industry": Proceedings of the FPRS meeting January 1979 i n Seattle: FPRS Madison, Wisconsin 1979.

15.

T. B. Reed - Personal Communication.

16. Overend, R. "Gasification an Overview" i n "Retrofit 1979" Edited by T. B. Reed and D. E. Jantzen SERI/TP-49-183: Golden Colorado 1979. 17. Biomass Energy Institute Inc. "Biogas Production from Animal Manure," Biomass Energy Institute: Winnipeg, 1978.


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Burford, J.; Varani, F.T. Design and Economics of Lamar, Colorado Bioconversion Plant," CSM Mineral Indusries Bull., V21 (no 4): Golden Colorado 1978. Moon, G.D.; Messick, J . R . ; Easley, C . E . ; Katzen, R. "Technical and Economic Assessment of Motor Fuel Alcohol from Grain and other Biomass," Report to U.S. DOE - Contract EJ-78-C-01-6639; Washington, D.C. 1978.

RECEIVED

December 18, 1979.


Canada's Biomass Conversion Technology R&D ... - ACS Publications

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