- Statement of Changes in Beneficial Ownership (4)

FORM 4 [ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person * DIESCH JOHN HOWARD	2. Issuer Name and Ticker or Trading Symbol RENTECH INC /CO/ [ RTK ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director                      _____ 10% Owner __ X __ Officer (give title below)      _____ Other (specify below) Senior Vice President
(Last)          (First)          (Middle) 10877 WILSHIRE BLVD., SUITE 600	3. Date of Earliest Transaction (MM/DD/YYYY) 10/4/2012
(Street) LOS ANGELES, CA 90024 (City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) _ X _ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. Code (Instr. 8)		4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	10/4/2012		M		23529	A	$0	141641	D
Common Stock	10/4/2012		F		7313	D	$2.54	134328	D

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Option to Purchase Common Stock	$4.15							7/14/2009	7/13/2016	Common Stock	40000		40000	D
Restricted Stock Units	$0							(1)	11/3/2012	Common Stock	85826		85826	D
Restricted Stock Units	$0							(2)	11/17/2012	Common Stock	66667		33334	D
Restricted Stock Units	$0							(3)	12/10/2012	Common Stock	16538		16538	D
Restricted Stock Units	$0   (4)	10/4/2012		M			23529	(4)	10/4/2013	Common Stock	70588	$2.54	23530	D
Option for Common Stock	$.95							(5)	10/4/2020	Common Stock	164706		164706	D
Restricted Stock Units	$0   (6)							(6)	10/12/2014	Common Stock	95000		95000	D
Performance Stock Units	$0   (7)							(7)	10/12/2014	Common Stock	190000		190000	D
Restricted Stock Units	$0   (8)							(8)	11/9/2014	Common Stock	194780		194780	D

Explanation of Responses:
( 1)	Each restricted stock unit represents a contingent right to receive one share of common stock. 47,681 restricted stock units are vested in consideration for the reporting person allocating a portion of his fiscal year 2008 cash bonus to purchase such units and the remaining 38,145 restricted stock units vest on November 3, 2012, subject to the reporting person's continued employment with the Company on such date.
( 2)	Each restricted stock unit represents a contingent right to receive one share of common stock. One-third of the restricted stock units vested on November 17, 2010, one-third vested on November 17, 2011 and the remaining one-third will vest on November 17, 2012, subject to the reporting person's continued employment with the Company on such date.
( 3)	Each restricted stock unit represents a contingent right to receive one share of common stock. Fifty percent of the restricted stock units are vested in consideration for the reporting person allocating a portion of his or her cash bonus to purchase such units at the fair market value of $1.69 per unit based on the closing price of the Company's common stock on December 10, 2009, and the remaining fifty percent vest on December 10, 2012, subject to the reporting person's continued employment with the Company on such date.
( 4)	Each restricted stock unit represents a contingent right to receive one share of common stock. One-third of the restricted stock units vest on each of the first three anniversaries of October 4, 2010, subject to the reportins person's continued employment with the Company on each such date.
( 5)	The option vests in three equal installments of common stock on the first, second and third anniversaries of the grant date (October 4, 2010), subject to reporting person's continued employment with the Company on each such date.
( 6)	Each restricted stock unit represents a contingent right to receive one share of common stock. One-third of the restricted stock units vest on each of the first three anniversaries of October 12, 2011, subject to the reporting person's continued employment with the Company on each such date.
( 7)	Each performance stock unit represents a right to receive one share of common stock. One hundred percent of the performance stock unit will vest upon the Company's value weighted average price for a 30 day period equaling $3.00 or more on or prior to October 12, 2014.
( 8)	Each restricted stock unit represents a contingent right to receive one share of common stock. One-third of the restricted stock units vest on each of the first three anniversaries of November 9, 2011, subject to the reporting person's continued employment with the Company on each such date.

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
DIESCH JOHN HOWARD 10877 WILSHIRE BLVD., SUITE 600 LOS ANGELES, CA 90024			Senior Vice President

Signatures
/s/ John H. Diesch		10/9/2012
** Signature of Reporting Person		Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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