From Aquatfs@aol.com Mon May 15 15:18:37 2000 Date: Mon, 15 May 2000 10:54:56 EDT From: Aquatfs@aol.com To: sanet-mg@cals.ncsu.edu Subject: Re: Biological Digesters I would like to add a cautionary note concerning aerobic and anaerobic digesters. As I am sure you can appreciate being in the farming related business, digesters are biological systems that require careful monitoring and operation in order to be successful. When one of these systems crashes, it can take weeks to return the system to a healthy steady state operating condition. Microorganisms can be quick to multiply under good conditions, slow to multiply under sub-optimal conditions, but are even quicker to die under poor operating conditions. Digesters work best under reasonably constant flows (if continuous) and loading. Intermittent operation is not easy to achieve. Significant changes in the make up of the inputs can lead to significant changes in the operation and outputs. It takes considerable experience to run a digester efficiently. Performance data will be very much dependent on the expertise of the operator, environmental factors (such as temperature), and the quality and mix of inputs. A break down of a tractor or other farm implement is generally not going to result in a catastrophic failure of the crop. A break down in a component of a digester can result in a rapid failure of the system. Having stated these cautions, I would al;so like to add that digesters are a proven technology. However, they require careful scrutiny and maintenance of the operating parameters and a TRAINED operator to maintain the system and detect problems BEFORE the system crashes. In the event where you are dependent on the digester for disposing of waste materials, what will you do with this waste if your system crashes for several weeks? Do you have a storage option or contingency plan? These are additional considerations to include in evaluating digesters. Alan Ismond, P.Eng. Aqua-Terra Consultants To Unsubscribe: Email majordomo@cals.ncsu.edu with the command "unsubscribe sanet-mg". If you receive the digest format, use the command "unsubscribe sanet-mg-digest". To Subscribe to Digest: Email majordomo@cals.ncsu.edu with the command "subscribe sanet-mg-digest". All messages to sanet-mg are archived at: http://www.sare.org/san/htdocs/hypermail