Louis Zsuffa

Methane fermentation of woody biomass

Abstract Woody biomass has been previously considered to be highly refractile to anaerobic digestion without extensive pretreatment. However, this study has demonstrated that high rates and ultimate methane yields may be obtained in batch assays without pretreatment, other than some particle size reduction. In a survey of 32 woody samples (chiefly willow and poplar species grown in a wood-grass system) significant yields of methane (≥ 0·25 liters g−1 volatile solids added) were obtained from 19 of the samples, while the yield from 3 of the samples (Salix eriocephala, S. exigua and Platanus occidentalis) exceeded 0·30 liters g−1 volatile solids added. The commercial production of energy through the biological gasification of woody biomass may therefore represent a viable alternative for energy production in the United States. An interesting feature of this study was the biphasic nature of methane production from two-thirds of the samples tested.

Genetic improvement of willows for energy plantations

Abstract Seven countries participated in the 3-year programme (1986–1988) of the Willow Breeding Activity, Task 2 of the International Energy Agencys Bioenergy Agreement. The objectives of the activity were to facilitate the development of superior, high yielding willow clones for energy plantations by (a) exchange of genetic stock, (b) exchange of information on breeding studies, and (c) joint actions. The results of this cooperative activity are discussed accordingly. Significant achievements are in (a) enrichment of the genetic stock, especially of North American willow species; (b) evaluation and stimulation of genetic studies and breeding programmes; and (c) joint actions on disease surveys, clonal identification problems, joint testing methods and willow feedstock qualities for energy conversion. The development of high yielding stock (30 odt/ha per year or more) seems to be within reach.

Screening Populus deltoides marsh. selections by allozymes to assure species identity

The allelic constitution of 169 Populus deltoides Marsh, clones, selected in North America, was studied at 8 marker allozyme loci (Aco‐2, Mdh‐2, Pgi‐2, Pgm‐1, Pgm‐3, 6‐Pgd‐2, 6‐Pgd‐4 and 6‐Pgd‐5) coding for 5 enzyme systems in root tips. The enzymes were assayed by horizontal starch gel electrophoresis. An examination of the allozyme profiles revealed that twenty‐seven of these selections (16%) were misidentified as P. deltoides. Eighteen of the misidentified selections displayed isozyme genotypes and patterns typical of P. deltoides x P. higra L. hybrids (P. xcanadenis Moench) and the remaining nine selections typical of P. deltoides x P. balsamiferaL. (P. xjackii Sarg.). The results indicated a need for screening North American P. deltoides selections used for plantation, breeding, and biological studies to assure their accurate species identification. Allozyme markers can be of potential importance in detecting misidentified P. deltoides specimens and in ascertaining their correct species identity.

Biomass qualities and potential for genetic improvement in poplars and willows

Abstract Systems for growing woody lignocellulosic materials on short rotation on agricultural land are described. Potential uses for this biomass are outlined and related to the characteristics of the harvested material. The role of genetics and silvicultural manipulation in generating new and more appropriate feedstocks is discussed. Recommendations for necessary research and development to develop the potential for short rotation production systems for lignocellulosics are given.

Genetic relationship between Salix exigua and other North American willows (Salix L.): Evidence from allozyme variation

Abstract Starch gel electrophoresis was used to examine the allozyme variation and the genetic relationship between Salix exigua and other North American willows. A total of 149 clonal collections comprising six willow species were analyzed for 26 putative isozyme loci. Genetic distances between species were estimated and used for distance analysis of species relationships. Individual alleles were used as characters for cladistic analysis of phylogenetic inference. Distance analysis indicates that S. exigua has approximately equal divergence to both subgenus Salix and Vetrix . Results of cladistic analysis suggest that S. exigua may be a separate group isolated from all other willows. Based on evidence of allozyme variation, it is suggested that the taxonomic placement of S. exigua within subgenus Salix need to be revised.