Medical brain Notes 9

  Biotechnology and Waste Waste represents one of the three key inter-vention points for the potential use of environmental biotechnology. Moreover, in many ways this particular area of application epitomises much of the whole field, since the management of waste is fundamentally unglamorous, typically funded on a distinctly limited budget and has traditionally been viewed as a nec-essary inconvenience. However, as the price of customary disposal or treatment options has risen, and ever more stringent legislation been imposed, alternative technologies have become increasingly attractive in the light of their greater rel-ative cost-effectiveness. Nowhere has this shift of emphasis been more apparent than in the sphere of biological waste treatment.  With all of environmental biotechnology it is a self-evident truism that what-ever is to be treated must be susceptible to biological action and hence the word ‘biowaste’ has been coined to distinguish the generic forms of organic-o...

  The Nature of Biowaste Biowaste arises from a number of human activities, including agriculture, hor-ticulture and industry, broadly falling into one of the following three major categories: faeces/manures, raw plant matter or process waste. This fits neatly into the process-orientated approach mentioned above, since the general char-acteristics of each are such that biological breakdown proceeds in essentially the same manner within the group and, thus, the ease of their decomposition is closely similar. Although, at least chemically speaking, biowaste can be seen as being characterised by a high carbon content, this definition is so wide as to include the vast majority of the substances for which all environmental biotech-nologies are viable process options. Hence, in the present discussion, biowaste is limited to substances which have been derived from recently living matter, with the approaches available to deal with other carbon-rich materials having already been examined in...

  Composition of biowaste Biowaste of animal origin such as that contained in sewage and soiled animal bedding contains unabsorbed fats, proteins and carbohydrates, resulting from incomplete digestion of ingested food of animal and plant origin. In addition, abattoir waste would include all of the above and a substantial proportion of fats and protein, derived from the slaughtered animal. In addition, materials excreted by the animal include metabolic breakdown products such as urea and other small nitrogen-containing materials, for example partially degraded bile pigments. Live and dead bacteria, normally resident in animal gut are also present in the biowaste and so contribute their own fats, proteins, carbohydrates and nucleic acids.  In addition to all the components listed above, biowaste of plant origin will contain cellulose, hemicelluloses and lignin. Cellulose is worthy of note given that estimates of over 50% of the total organic carbon in this biosphere is to be fou...

  Biological Waste Treatment The aims of biological treatment are relatively straightforward and can be summed up in the following three points: 1.          Reducing the potential for adverse effects to the environment or human health. 2.          Reclaiming valuable minerals for reuse. 3.          Generating a useful final product. Broadly speaking, this effectively means the decomposition of the biowaste by microbes to produce a stable, bulk-reduced material, during which process the complex organic molecules originally present are converted into simpler chemi-cals. This makes them available for literal recycling in a wider biological context.  To some extent these three aims can be seen as forming a natural hierarchy, since removing environmental or health risks, and deriving a stable product, forms the bottom rung of the ladder for all biological waste tr...

  Composting For centuries, gardeners and horticulturalists have encouraged biodegradable waste to break down to produce stable, nutrient-rich compost for use in pots or directly for improving the soil. This application of the natural, exothermic process of aerobic decomposition, is familiar and time-honoured. More recently, however, composting has been the recipient of increased attention as a poten-tial means of treating biowaste on a municipal basis. Though the scale of such operations imposes certain restrictions of its own, generally, putrescible matter decomposes more efficiently and completely when oxygen is readily available. This leads to proteins being degraded to nitrogen or ammonia and ultimately mineralised to nitrate, while fats and carbohydrates are broken down to carbon dioxide and water, via organic acids. This is, of course, purely a mass flow overview of the process since a proportion of the material becomes incorporated into microbial cells, as the decomposers t...

  Applying Composting to Waste Management Composting has an appeal to local authorities needing to meet diversion targets while keeping a watch on their budgets, since it is relatively simple and does not demand particularly high resource investment, either to set up or run. As a consequence, many of the initiatives instigated to deal with biowaste have been based on composting of one form or another. In the broadest of terms, such schemes fall into one of two categories, namely, home composting, or centralised facilities. The focus of this section will fall on the latter, as a more representative application of biotechnology, though to set this in context, it is worth giving a brief outline of the former. Home composting Home-based systems differ little in reality from the traditional gardener’s approach, putting biodegradable material into a heap or, more typically a bin, often provided free or at a subsidised price, by the local council. Though this does have the advantage of di...