AMENDMENT NO. 1 WARRANT TO PURCHASE COMMON STOCK

Exhibit 4.16

AMENDMENT NO. 1

WARRANT TO PURCHASE COMMON STOCK

This Amendment No. 1 (this “Amendment”), is made and entered into effective as of June 30, 2005, by and between Rentech, Inc., a Colorado corporation (“Rentech”), and Monarch Pointe Fund, Ltd., Mercator Momentum Fund, LP, Mercator Momentum Fund III, LP, Pentagon Special Purpose Fund, Ltd. (collectively, the “Purchasers”) and M.A.G. Capital, LLC (“MAG”).

The parties hereby agree to amend the Warrant to Purchase Common Stock between Rentech and MAG and Rentech and each of the Purchasers dated April 8, 2005 (the “Warrant”) as follows:

Section 1.1 of the Warrant is deleted in its entirety and replaced as follows: “This Warrant is exercisable in whole or in part (but not as to any fractional share of Common Stock), at any time that is more than 181 days after the date of this Warrant (October 8, 2005) and from time to time thereafter prior to 6:00 p.m. on the Expiration Date set forth above.”

This Amendment may be executed in two or more counterparts and may be delivered by facsimile transmission, each of which shall be deemed an original, but all of which together constitute one and the same instrument.

IN WITNESS WHEREOF, the parties have caused this Amendment No. 1 to be executed by its duly authorized.

RENTECH, INC.						M.A.G. CAPITAL, LLC
By:		/s/ Xxxxxx X. Xxxxxxxx				By:		/s/ Xxxxx Xxxxxxxxx
Name:		Xxxxxx X. Xxxxxxxx				Name:		Xxxxx Xxxxxxxxx
Title:		President and CEO				Title:		Managing Member

MONARCH POINT FUND, LTD.						MERCATOR MOMENTUM FUND, LP
By:		/s/ Xxxxx Xxxxxxxxx				By:		/s/ Xxxxx Xxxxxxxxx
Name:		Xxxxx Xxxxxxxxx				Name:		Xxxxx Xxxxxxxxx
Title:		Managing Member				Title:		Managing Member

MERCATOR MOMENTUM FUND III, LP						PENTAGON SPECIAL PURPOSE FUND, LTD
By:		/s/ Xxxxx Xxxxxxxxx				By:		/s/ Xxxxxxxx X. Xxxxx
Name:		Xxxxx Xxxxxxxxx				Name:		Xxxxxxxx X. Xxxxx
Title:		Managing Member				Title:		Director