An “entremanure” (entrepreneur + manure) is someone who makes money from manure—usually from its use as fertilizer. “Entremanure” has been cited in print since at least 1985, and was entered in the Urban Dictionary in 2006.
 
“I started a business that sells fertilizer. I guess you could say I’m an… Entre-manure” was posted on Reddit—3amjokes on September 18, 2017.
     
             
31 March 1985, Richmond (VA) Times-Dispatch, “Lawn expert makes grass greener” by Jerry Lazarus, pg. E1, col. 3:
He says his friends call him an “entremanure” rather than an entrepreneur because he makes his living spreading composted waste on lawns to restore the missing ingredient in the soil, humus or organic matter.
 
13 February 1988, Huntsville (AL) Times, “Unique power plant no cow-pie-in-the-sky for ‘entremanure’” by Lee Siegel, pg. 1, col. 2:
LOS ANGELES—A desert power plant burns enough cow dung to electrify up to 20,000 homes, thanks to 250,000 cattle, $37 million in tax-exempt bonds and an environmentalist lawyer seeking his fortune as an “entremanure.”
 
14 February 1989, Chicago (IL) Tribune, “Sweets for the sweets” by Richard Phillips, pg. 16:
It’s a smelly business but a big moo-ver, avers California “entremanure” Will Parish, who built a desert power plant to convert cow manure to electricity.
 
12 March 1993, Lancaster (PA) New Era, “‘Fecal figurines’ a fertile field for entre-manureship” by Beth Davis:
John Rothman calls his creations “fecal figurines” and himself an “entre-manure.”
 
The New Jersey businessman and township committeeman is the creator of PooPets, a series of animal figurines made from cow manure.
   
Urban Dictionary
entremanure
An individual owner of a small, start-up business who is, in the end, totally full of shit; a new business owner who lacks experience in management, marketing, accounting, etc.; a business owner who develops or markets a “new” product that is utterly useless, ridiculous, or just plain stupid. Variations include “entremanurial” (adj.), entremanurism (n.)
(...)
by T. McGrimace March 08, 2006
   
YouTube
Ernest in ‘Entremanure’
knowwhatimeanvern
Published on Nov 14, 2007
One of many great commercials made back in the 80s starring yours truly, Ernest P. Worrell.
 
Twitter
Art Allen‏
@punsultant
Replying to @myklroventine
@myklroventine ha! What do you call a farmer who starts his own fertilizer business? An entremanure.
4:49 PM - 19 Oct 2009
 
Twitter
Jared G.‏
@Rob_Zincone
Thinking about starting a cutting-edge fertilizer business. I consider myself an entremanure.
12:24 PM - 13 Jun 2010
 
Twitter
brandon avance‏
@brandonavance
Replying to @buzzshift
@BuzzShift You know what they call someone starting a business in fertilizer?  An entre-manure.  #badjokefortheday
10:51 AM - 13 Apr 2011
 
Twitter
ryan m. brewer‏
@ryanmbrewer
i wish there was a self made business owner in the fertilizer field who’s twitter bio called him an entremanure.
1:47 PM - 23 Oct 2011
 
Twitter
Vermithrax Pejorativ‏
@Temmogen
does that mean that the guy who starts his own fertilizer business is an EntreMANURE?
9:59 AM - 21 Sep 2012
 
Reddit—3amjokes
I started a business that sells fertilizer… self.3amjokes
Submitted September 18, 2017 by knox_vile
I guess you could say I’m an… Entre-manure.