[Digestion] slurry from Potassium hydroxide catalyzed glycerin

[Douglas Renk]

Hello Anand- Thanks for your reply and the information on the salt tolerance of the ornamentals and such. 4% salinity is greater than most seawater, very impressive. The levels of sodium ions in the digester will likely never reach 0.4%. Rainfall in my region of North America prevents any issues related to prolonged application of digestate with this concentration. 

I have received some helpful response and research on AD and salt tolerant microbial cultures.

Best wishes,
Doug




________________________________
 From: Anand Karve <adkarve at gmail.com>
To: david at h4c.org; For Discussion of Anaerobic Digestion <digestion at lists.bioenergylists.org> 
Sent: Wednesday, January 4, 2012 9:23 PM
Subject: Re: [Digestion] slurry from Potassium hydroxide catalyzed glycerin
 

Dear Douglas,
there are many economically useful plants that tolerate about 4% saliniy in the root zone. I can only name the tropical ones. They are coconut, casuarina (timber), Thespesia populnea ((timber), Salvadora oleoides (oilseed), a number of mangrove species (timber, firewood), many plants belonging to the family chenopodiaceae (leafy vegetables), etc. If you used salt water for irrigation in a normal field, the water evaporates and the salt accumulates in the soil. The increased salinity ultimately kills the plants. But if these plants are planted in raised beds offering good drainage of water, the excess salt is washed away with every irrigation and the plants survive. I have demonstrated that these plants can even be irrigated with untreated seawater. One uses so much sea water for irrigation, that a part of it drains out of the beds and flows back into the sea.
Yours
A.D.Karve 


 
On Thu, Jan 5, 2012 at 8:02 AM, David <david at h4c.org> wrote:


>Douglas,
>
>On 1/4/2012 7:15 AM, Douglas Renk wrote: 
>Has anyone demonstrated the effect of introducing marine anaerobes highly toleratant of sodium into glycerin by-product enhanced digesters? Sodium may still be of concern for land application, but perhaps the digester could remain stable. I recall some studies about 20 years ago with Chynoweth at IGT for inoculum suited for sea kelp digestion. 
>> 
>>Any experience with this may greatly help our biogas industry with co-digestion of biodiesel glycerin. I find the industry resistant to move away from sodium hydroxide catalyst.
>In a study about the digestion of (apparently salty) Korean food wastes ("Effect of particle size and sodium ion concentration on anaerobic thermophilic food waste digestion" Water Sci Technol. 2000;41(3):67-73), Kim et al found that 
>
>
>...methane gas production [was] affected by various sodium ion concentrations. The reaction was not affected until 5 g/L of sodium ion was added into the test reactor. The volume of methane gas produced from the test reactors decreased gradually according to the sodium ion concentrations applied when more than 5 g/L of sodium ion. In case of 20 g/L of sodium ion, the methane gas production was reduced to about 50% of theoretical gas volume.
>>
>Of course, as you imply, a good deal depends on the population in the digester, but given that glycerin is so easily acidified, that it is more easily produces stable digestion when other materials are added to the digester, and that it must in any case be fed slowly, it seems unlikely that the first problem one would encounter would be sodium ion concentration. In other words the circumstances that lead to stable digestion would tend likewise to reduce sodium concentration in the digester, except perhaps if it is fed kelp or a similar high-sodium co-digestate. As far as Wayne's question about ag use of sodium-"enriched" effluent, that I would think would depend primarily on the circumstances. Sodium would be a problem particularly in drier climates and soils.
>
>
>d. 
>-- 
>
>David William House
> 
>"The Complete Biogas Handbook" www.completebiogas.com
>Vahid Biogas, an alternative energy consultancy www.vahidbiogas.com
>
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>
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-- 
***
Dr. A.D. Karve
Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)



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