TENHUNEN@finujo.bitnet (03/29/89)
From: Lasse Johansson, Engineer Firm Ekodesign Pallastunturinkuja 7 G 25 SF-01280 Vantaa FINLAND Tel: Int. 358-0-3920186 *************************************************** *EXCESSIVE AERATION - A COMMON ERROR IN COMPOSTING* *************************************************** In literature and in practical composting applications, the importance of powerful aeration has been generally stressed. Air exchange is of course inevitable, but in a considerable less degree than in the current practice. This can be cleared by comparing the two areas inside the compost that has just been made and mixed so that its mois- ture and nutrient proportions are suitable, and it has just reached the optimum temperature area. In this situation the INNER PART produces heat actively, and the convection of the heat is prevented by a thick layer of compost biomass around it. This same layer also SLOWS DOWN the excessive gas exchange and reduces its chilling effect. The SURFACE PART again receives continuously excess heat from the warmer inner part, and it is chilled and dried by the surrounding, freely moving air. The reactors made according the current recommendations for forced composting have been constructed mainly to imitate the conditions of this surface part. A good example of this are the electric, so called "rapid composting privies", where the aeration has been forced by a blower, and the mis- sing heat insulation is aimed to compensate by electric hea- ting. These two actions - that both need extraneuous energy - aim in a great deal to cancel each other. So the wished effect, the promotion of the composting process, becomes difficult. This disadvantage will again be accentuated, if the mixing will work badly or is wholly missing. The moisture and the composting aid can be distributed in the mass very unevenly. The particles with deviating specific mass - e.g. paper - can even be left wholly unmixed, because the surface dried by the too efficient air exchange will lose part of its sticking and covering properties. The same errors can be found in the unheated containers of direct composting privies and - in general - in household waste composters. The drawback effects of incomplete mixing will be aimed to compensate by the too effective aeration. The chilling effect will delay the process, and this makes one again to scale up the size of the unit, so that the price will rise and operation and maintenance will become more difficult. The process could be forced by reducing aeration and by inc- reasing heat insulation and mixing. So, the unit size could be scaled down. Joining this with good technical and ergo- nomical planning practice, a product can be designed that will both be a bestseller and add the proportion of ecolo- gical alternatives in our waste management practice. ******************************************* *Theory for a NEW COMPOSTING PRIVY DESIGN:* ******************************************* By imitating the conditions where the INNER PART of the well-working compost will reach its momentary temperature maximum and by aiming to maintain this stage as a continuous process, it is possible to develop a small and energy self- sufficient composting process. *** ORGANIZER'S COMMENT: Please send your possible comments to the BIO-CONVERSION bulletin board / newsgroup / teleconference system you'll use - or straight to me: Organizer: Juhani Tenhunen, M. Sc. (Eng.) University of Joensuu Karelian Institute, Section of Ecology Laboratory of Environmental and Energy Biotechnology P.O. Box 111 SF-80101 Joensuu FINLAND Telefax: Int. 358-0-1513590 Email: TENHUNEN at FINUJO (BITNET) ecoleeb at csc.FI (Internet) ecoleeb at fssc.funet (X.400) 12762:TBX723 (Dialcom) 19205723 tbx sf (Telex in Finland) E_Juhani_Tenhunen at com.Helsinki.FI (PortaCOM Net) cdp!gn!ejtenhunen%LABREA at STANFORD.BITNET (EcoNet) ejtenhu at cosy.uoguelph.CA (CoSy at Guelph) JOYL::TENHUNEN (DECnet/NORDUNET) funet:joyl::tenhunen (Finnish ELISA) Sent for: BIO-CONV at IRLEARN.UCD.IE en.bioconversion (EcoNet/Greennet) bioconversion/composting (CoSy at Guelph) Mail copy (incl. original in Finnish): Jarmo Louvo Tapio Raita Arto Salokangas Mirja Salkinoja-Salonen Arja Vuorinen Arto Stenroos Sirkka Malkki George Woolston Raimo Lilja Rainer Lahti