cleanworld<\/a>, a private company with which uc davis partnered to produce the machine.<\/p>\n\u201cthe digester is basically a vertical hammer mill,\u201d zhang says, referring to a machine that crushes and shreds material through the repeated blows of little hammers.<\/p>\n
read is composed of four tanks. three of them are for breaking up and pulverizing waste. the digester first separates any plastic that does not belong. it then grinds the food waste and organic material into a paste, which is pumped into the first tank.<\/p>\n
\u201cthe first tank has bacteria that break food waste down into organic acid,\u201d zhang says. \u201cthen (it) goes into the second tank, which has high density microbes that convert organic matter into gas.\u201d<\/p>\n
the fourth tank is where the digestate, or leftover organic matter, is stored.<\/p>\n
\u201cthe leftovers have all the nutrients,\u201d zhang says.<\/p>\n
zhang developed this technology 10 years ago at uc davis and was able to turn the plans into action with the help of cleanworld, which specializes in biodigesters. the university took over full operation of the digester in early 2018, with zhang as a liaison between cleanworld and uc davis, and is now investing more into the operation.<\/p>\n
it\u2019s also an easy way for local restaurants, farms and communities to dispose of waste for between $35 and $52 per ton.<\/p>\n
uc davis is a non-profit, but zhang says her operation \u201cis a full business model.\u201d<\/p>\n
\u201ceconomically, we\u2019re not getting any money back,\u201d she says. \u201cwe got funding from [the] state to create these. it\u2019s not about money, it\u2019s about the show and tell, and making it work.\u201d<\/p>\n
even though zhang and her team are not making money, that\u2019s not to say others couldn\u2019t.<\/p>\n
\u201cthis is a great example of taking the technology forward and making a commercial business,\u201d she says.<\/p>\nat a woodland, calif., commercial farm, tomatoes that were left behind after harvest remain on the ground as a way to fertilize the ground for next year’s crop. whether a synthetic or biofertilizer, farms will use nutrients to boost their crop production over the course of a season. (katherine baker\/columbia university)<\/figcaption><\/figure>\nzhang and her team give the fertilizer they make to area farms who then report the results back to them. a 2-year-long study on digestate fertilized tomatoes yielded results comparable to tomatoes fertilized with uan-32, a popular synthetic fertilizer, which is 32% nitrogen.<\/p>\n
\u201cyields for the digestate fertilizers were equal to the uan-32 and even higher in the case of the digestate concentrate,\u201d edalati says. \u201cthe digestate fertilized tomatoes had higher soluble sugar content than the uan-32 tomatoes.<\/p>\n
\u201cuan-32 is good for providing nitrogen, but does not give you anything else. plants also need more than just nitrogen. digestate can provide that.\u201d<\/p>\n
zhang and her team want to ship the digestate farther than they are currently able to.<\/p>\n
\u201cthe digestate is valuable, but transporting it is not necessarily economically viable,\u201d edalati says of the liquid fertilizer. \u201cthe pellets would be one way to be able to transport nutrients far away at a cheaper cost.\u201d<\/p>\n
the difficulty lies in nitrogen content. the liquid digestate is 5% to 6% nitrogen \u2013 an essential component to fertilizer \u2013 whereas the pellet form is only 0.1 percent to 0.3 percent nitrogen. \u201cyou\u2019d have to transfer a lot more of this to get the same amount of nitrogen,\u201d edalati says.<\/p>\n
neither, though, compare to uan-32, the popular synthetic commercial fertilizer.<\/p>\n
\u201cyou can literally apply a couple hundred milliliters of uan-32 versus hundreds of gallons of (digestate),\u201d edalati says. \u201cthat\u2019s the challenge.\u201d<\/p>\nedalati holds up the liquid digestate, or biofertilizer, in glass jars. this made it easy to see the differences in color and particulates, from various stages in the anerobic process. (justin rex\/texas tech university)<\/figcaption><\/figure>\nthankfully, though, they have a virtually endless supply of test material while they work out how to make their fertilizer more nitrogen-rich.<\/p>\n
\u201cice cream, muscle milk, tomato paste and cut tomatoes from campbell\u2019s,\u201d he says with a laugh, listing some of the more frequent items from which he\u2019s made fertilizer. \u201call of those used to go to a landfill. now they come here.\u201d<\/p>\n
\u201ccoffee, too,\u201d zhang adds. \u201cwe put a lot of coffee in here. maybe those bacteria love it and get energized.\u201d<\/p>\n
\n <\/p>\n","protected":false},"excerpt":{"rendered":"
next in our tackling food waste series: what if you could take food waste and give it another life \u2014 or two? that’s the idea behind the biodigester facility at uc davis. university of wisconsin-madison’s peter jurich reports.<\/p>\n","protected":false},"author":9584,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4907,4902,4896,5196],"tags":[112,2519,4117,1793,129,4078,591,81,2545,4079],"storyfest_categories":[],"class_list":["post-12103","post","type-post","status-publish","format-standard","hentry","category-business-economics","category-colleges-education","category-food","category-past-storyfest","tag-agriculture","tag-anaerobic-digester","tag-biodigestion","tag-fertilizer","tag-food-waste","tag-pfincali","tag-storyfest","tag-sustainability","tag-synthetic-fertilizer","tag-woodland"],"acf":[],"yoast_head":"\n
biodigester transforms food waste into fertilizer, energy - planet forward<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n