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The uranium-adsorbing abilities of seven plant wastes were investigated. High abilities to adsorb uranium from non-saline water containing 10 mg dm⁻³ of uranium were observed with a number of plant wastes tested. However, with seawater supplemented with 10 mg dm⁻³ of uranium, similar results were found only with chestnut residues. When the plant wastes were immobilized with formaldehyde, their ability to adsorb uranium was increased. Uranium and copper ions were more readily adsorbed by all plant wastes tested than other metal ions from a solution containing a mixture of seven different heavy metals. The selective adsorption of heavy metal ions differs with different species of plant wastes. The immobilization of peanut inner skin, orange peel and grapefruit peel increased the selectivity for uranium.

Three countries participated in the ‘Poplar Exchange’ activity of the 3-year programme of Task 2 of the International Energy Agency's Bioenergy Agreement. The objectives of this activity were to exchange clones and/or seeds for immediate use in new environments and to collect information on clonal reactions to various diseases in different environments. Discussed in this paper are the poplar breeding programme in Belgium, biomass production possibilities, clones exchanged, current outstanding problems, and provisional results.

The application of systems analysis in evaluating biomass energy supply systems in member countries within the International Energy Agency (IEA) Bioenergy Agreement is discussed. A review of the state of the art was given at an international workshop, arranged at the Swedish University of Agricultural Sciences in Garpenberg, 6–7 June 1988. The workshop covered a wide range of applications and clearly demonstrated the large variety and viability of existing concepts. The energy supply situations and policies of different countries strongly influence the directions in which systems are developed. Established methods for systems and economic analysis are sufficient as long as the applications are on the systems or corporate levels. Evaluations are more difficult on the national level. The neoclassical economic theory has severe shortcomings, when considering long range aspects on limited resources.

2-Fluraldehyde was converted into 2-(5-R-2-furyl)-1, 3-dioxanes; 5-R-2-cyanofurans where R = H, Br, I or NO₂; bis(5-bromo-2-furyl-1,2-R diimine where R = ethyl or butyl; and 5-hydroxymethyl-2-furaldehyde. Furfuryl alcohol, obtained from 2-furaldehyde by the Cannizaro reaction, and 5-hydroxymethyl-2-furaldehyde were reacted with hydrogen sulphide to give 2,2′-difurfuryl thioether in 5% yield and thiobis (5-methyl-2-furaldehyde) in 6% yield, respectively. Furfuryl alcohol reacted with 5-hydroxymethyl-2-furaldehyde to yield 5-formyl-2,2′-difurfuryl ether in 6% yield. The dioxanes were found to decompose when stored at room temperature for more than six months, while the other compounds were relatively stable when stored for the same period of time.

Qualitative analysis of 33 mountain tree and shrub species which grow in the Garhwal Himalaya indicated that temperate species are better suited as fuelwood species as they contain high density wood, low ash content and low N-percentage. The fuelwood value index showed that Premna barbata from a tropical area had a high calorific value, low ash content, low nitrogen percentage and thus has the highest value. The most promising species were Pyracantha crenulata, Daphniphyllum himalense, Lyonia ovalifolia, Cotinus coggygria, Cotoneaster affinis and Prunus spp.

The kinetic models proposed by Monod, Chen and Hashimoto and Singh as well as those of a first order and diffusional type have been tested for fit as mathematical descriptions to describe substrate utilization during anaerobic digestion of the organic fraction of source sorted municipal solid waste. A new model, described as step diffusional, is proposed and the results obtained with it are compared with those obtained using previously published models. The new model is found to show a better fit to the experimental result than those obtained with other models. The new model takes into account simple qualitative and quantitative chemical characteristics of the substrate to be digested. Although this new model is more complex than some others since it involves four kinetic constants, conceptually it is simple enough to find practical applications.

A lignin has been isolated from a prototype hardwood, Populus deltoides, by organosolv delignification using ethylene glycol, followed by dilute acidification of the spent black liquor. Various approaches for product separation are described. It was found that separation of the product slurry was best achieved if suction filtered whilst hot (> 100°C). The effects of temperature, volume ratio of black liquor/acidic aqueous solution, and acid concentration for precipitation of the lignin are discussed. Optimum conditions, in terms of yields, filterability, texture and color of the lignin were found to be: temperature range 50–60°C, liquor/acid volume ratio 1:3 and an acid concentration of 0·05%wt aqueous hydrochloric acid. The glycol lignin so isolated was soluble or partly soluble in a number of organic solvents. Gel permeation chromatography showed the weight average molecular weight to be 4762 g/mole with a polydispersity of 4·8 and the elution profile indicated a significant proportion of this lignin consists of a low molecular weight material. ¹³C NMR spectroscopy suggested that some cleavage of β-aryl ether linkages during the solvolysis process had occurred. This lignin seems to be rich in aliphatic hydroxyl groups and syringyl units. The presence of a strong signal at low field in the aliphatic region of the NMR spectrum suggests its origin from the solvent due to a possible ‘lignin-solvent interaction’ that occurred during the delignification step. Electron microscopy showed the lignin to exist as aggregates of mostly spherical particles of size range 0·5–2·5 μm.

A seminal paper by Mobil researchers in 1979 demonstrated that a remarkable range of materials were convertible to a similar, high-octane, aromatic, gasoline product slate when passed over HZSM-5, a medium-pore, shape-selective, acid catalyst. These materials ranged from low molecular weight oxygenates, such as methanol, to high molecular weight latexes and vegetable oils. In this paper, we briefly review the thermochemical conversion options for algal and vegetable lipids, present the potential advantages of the zeolite approach and consider the possibility of converting either the whole algae or vegetable oil seed, or crudely extracted lipids, to a product virtually indepedent of fatty acid composition of the lipid. Experimental data on pyrolysis, and on product slates and yields over H-ZSM5, are shown for rapeseed oil, tripalmitin and algal lipids. The pyrolyzer-catalytic reactor, and the ambient pressure, molecular beam, mass spectrometric analytical sampling system, are shown and briefly described.

Municipal solid waste (MSW) conversion — the recovery of energy (and materials) from MSW — has been the subject of one activity within the 1986–88 International Energy Agency Bioenergy Agreement. The participating countries have been Canada, Sweden and the UK, with the activity being led by Harwell Laboratory. The major aim of the work has been to establish a co-operative approach to the R&D undertaken in each country on MSW conversion. The emphasis has been on R&D which concentrates on technical and environmental aspects of energy (rather than materials) recovery. This has encompassed a wide range of technology options — mass combustion, production and combustion of refuse derived fuels, abstraction and utilisation of landfill gas, anaerobic digestion, and thermal processing.

The paper gives a summary of the approach taken in fulfilling the aims of the activity and summarises recent, current and proposed R&D programmes in each country. Proposals made at an expert workshop for specific co-operative ventures during 1989–91 are also summarised.

This report summarizes work done under the International Energy Agency Activity entitled “Developing the coppicing potential of selected hardwoods”. Altogether, 26 papers and publications have been prepared under this project, discussing a large number of coppicing mechanisms and factors of many important short-rotation hardwood tree species, the main emphasis being on birch, poplar, alder and willow.

Coppicing research is reviewed briefly on the basis of two inquiries. There were 20 research projects and a total of 39 researchers dealing with coppicing in the various participating countries. A survey of coppicing problems indicates a need for scientific projects in ecophysiology, anatomy and stand dynamics.