Exhibit 99.1

FOR IMMEDIATE RELEASE

CASELLA WASTE SYSTEMS, INC. ANNOUNCES FIRST QUARTER FISCAL YEAR 2013 RESULTS

RUTLAND, VERMONT (August 29, 2012) — Casella Waste Systems, Inc. (NASDAQ: CWST), a regional solid waste, recycling and resource management services company, today reported financial results for its first quarter fiscal year 2013.

Highlights for the quarter included:

For the quarter ended July 31, 2012, revenues were $121.2 million, down $6.0 million or 4.7 percent from the same quarter last year, with positive collection pricing more than offset by lower solid waste volumes and lower recycling commodity prices.

The company’s net loss attributable to common shareholders was ($8.4) million, or ($0.31) per common share for the quarter, compared to net loss of ($3.1) million, or ($0.12) per share for the same quarter last year.

Operating income was $5.8 million for the quarter, down $4.5 million from the same quarter last year. The current quarter includes a $0.6 million expense related to the pending sale of the Maine Energy Recovery Company and certain financing costs. The quarter ended July 31, 2011 included a $1.0 million legal settlement charge. Adjusted EBITDA* was $24.3 million for the quarter, down $4.4 million from same quarter last year.

“During our first quarter recycling commodity prices weakened and we continued to experience declines in special waste volumes at our western New York landfills mainly due to decreased Marcellus Shale drilling activity,” said John W. Casella, chairman and CEO of Casella Waste Systems. “Despite these headwinds, I believe that we are executing well against factors that we can control in this challenging economic environment, such as:

“Weakness in the roll-off collection line-of-business offset much of gains we had in the residential and commercial lines-of-business,” Casella said. “The roll-off line-of-business was down in the quarter due to: pull forward of work into our fourth quarter with the early spring in the northeast, continued pressure on roll-off work because of depressed construction activity, and a tough comparison to the first quarter last year when we saw increased demand from flooding activity.”

“Nevertheless, we’ve reduced costs and realigned the way we operate, making us more efficient and more customer service-oriented, and putting us in a great position to prosper when economic conditions improve,” Casella said.

The company reaffirms guidance issued on August 10, 2012 for its fiscal year 2013, which began May 1, 2012, by estimating results in the following ranges:

The above guidance does not include the financial impacts from the potential sale of Maine Energy or the potential refinancing of the 11.0 percent $180.0 million second lien notes due July 2014 during fiscal year 2013.

*Non-GAAP Financial Measures

In addition to disclosing financial results prepared in accordance with Generally Accepted Accounting Principles in the United States (GAAP), the company also discloses earnings before interest, taxes, depreciation and amortization, adjusted for accretion, depletion of landfill operating lease obligations, gain on sale of assets, development project charge write-offs, legal settlement charges, bargain purchase gains, asset impairment charges, environmental remediation charges, as well as severance and reorganization charges (Adjusted EBITDA) which is a non-GAAP measure. The company also discloses earnings before interest, taxes, adjusted for gain on sale of assets, development project charge write-off, legal settlement charges, bargain purchase gains, asset impairment charges, environmental remediation charges, as well as severance and reorganization charges (Adjusted Operating Income) which is a non-GAAP measure. The company also discloses Free Cash Flow, which is defined as net cash provided by operating activities, less capital expenditures attributable to growth and maintenance (excluding acquisition related capital), less payments on landfill operating leases, less assets acquired through financing leases, plus proceeds from the sale of property and equipment, plus contributions from non-controlling interest holder, which is a non-GAAP measure. Adjusted EBITDA is reconciled to net income (loss), while Free Cash Flow is reconciled to net cash provided by operating activities.

The company presents Adjusted EBITDA, Adjusted Operating Income, and Free Cash Flow because it considers them important supplemental measures of its performance and believes they are frequently used by securities analysts, investors and other interested parties in the evaluation of the company’s results. Management uses these non-GAAP measures to further understand the company’s “core operating performance.” The company believes its “core operating performance” represents its on-going performance in the ordinary course of operations. The company believes that providing Adjusted EBITDA, Adjusted Operating Income, and Free Cash Flow to investors, in addition to corresponding income statement and cash flow statement measures, affords investors the benefit of viewing its performance using the same financial metrics that the management team uses in making many key decisions and understanding how the core business and its results of operations may look in the future. The company further believes that providing this information allows its investors greater transparency and a better understanding of its core financial performance. In addition, the instruments governing the company’s indebtedness use EBITDA (with additional adjustments) to measure its compliance with covenants such as interest coverage, leverage and debt incurrence.

Non-GAAP financial measures are not in accordance with or an alternative for GAAP. Adjusted EBITDA, Adjusted Operating Income, and Free Cash Flow should not be considered in isolation from or as a substitute for financial information presented in accordance with GAAP, and may be different from Adjusted EBITDA, Adjusted Operating Income, or Free Cash Flow presented by other companies.

About Casella Waste Systems, Inc.

Casella Waste Systems, Inc., headquartered in Rutland, Vermont, provides solid waste management services consisting of collection, transfer, disposal, and recycling services in the northeastern United States. For further information, investors contact Ned Coletta, vice president of finance and investor

relations at (802) 772-2239, media contact Joseph Fusco, vice president at (802) 772-2247, or visit the company’s website at http://www.casella.com.

Conference call to discuss quarter

The Company will host a conference call to discuss these results on Thursday, August 30, 2012 at 10:00 a.m. ET. Individuals interested in participating in the call should dial (877) 548-9590 or for international participants (914) 495-8541 at least 10 minutes before start time. The call will also be webcast; to listen, participants should visit Casella Waste Systems’ website at http://ir.casella.com and follow the appropriate link to the webcast. A replay of the call will be available on the company’s website, or by calling (855) 859-2056 or (404) 537-3406 (Conference ID 21047750) until 11:59 p.m. ET on Thursday, September 6, 2012.

Safe Harbor Statement

Certain matters discussed in this press release are “forward-looking statements” intended to qualify for the safe harbors from liability established by the Private Securities Litigation Reform Act of 1995. These forward-looking statements can generally be identified as such by the context of the statements, including words such as “believe,” “expect,” “anticipate,” “plan,” “may,” “will,” “would,” “intend,” “estimate,” “guidance” and other similar expressions, whether in the negative or affirmative. These forward-looking statements are based on current expectations, estimates, forecasts and projections about the industry and markets in which we operate and management’s beliefs and assumptions. We cannot guarantee that we actually will achieve the plans, intentions, expectations or guidance disclosed in the forward-looking statements made. Such forward-looking statements, and all phases of our operations, involve a number of risks and uncertainties, any one or more of which could cause actual results to differ materially from those described in our forward-looking statements. Such risks and uncertainties include or relate to, among other things: current economic conditions that have adversely affected and may continue to adversely affect our revenues and our operating margin; we may be unable to reduce costs or increase pricing or volumes sufficiently to achieve estimated Adjusted EBITDA and other targets; landfill operations and permit status may be affected by factors outside our control; we may be required to incur capital expenditures in excess of our estimates; fluctuations in energy pricing or the commodity pricing of our recyclables may make it more difficult for us to predict our results of operations or meet our estimates; we may incur environmental charges or asset impairments in the future; and we may be unable to sell our waste-to-energy facility and shift waste volumes to other landfill sites. There are a number of other important risks and uncertainties that could cause our actual results to differ materially from those indicated by such forward-looking statements. These additional risks and uncertainties include, without limitation, those detailed in Item 1A, “Risk Factors” in our Form 10-K for the year ended April 30, 2012.

We undertake no obligation to update publicly any forward-looking statements whether as a result of new information, future events or otherwise, except as required by law.

Investors:

Ned Coletta

Vice President of Finance and Investor Relations

(802) 772-2239

Media:

Joseph Fusco

Vice President

(802) 772-2247

http://www.casella.com

CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(Unaudited)

(In thousands, except amounts per share)

CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED BALANCE SHEETS

(Unaudited)

(In thousands)

CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(Unaudited)

(In thousands)

CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

(In thousands)

Note 1: Discontinued Operations

On January 23, 2011, we entered into a purchase and sale agreement and related agreements to sell non-integrated recycling assets and select intellectual property assets to a new company (the “Purchaser”) formed by Pegasus Capital Advisors, L.P. and Intersection LLC for $130,400 in gross proceeds. Pursuant to these agreements, we divested non-integrated recycling assets located outside our core operating regions of New York, Massachusetts, Vermont, New Hampshire, Maine and northern Pennsylvania, including 17 material recovery facilities (“MRFs”), one transfer station and certain related intellectual property assets. Following the transaction, we retained four integrated MRFs located in our core operating regions. As a part of the disposition, we also entered into a ten-year commodities marketing agreement with the Purchaser to market 100% of the tonnage from three of our remaining integrated MRFs.

We completed the transaction on March 1, 2011 for $134,195 in gross cash proceeds. This included an estimated $3,795 working capital and other purchase price adjustment, which was subject to further adjustment, as defined in the purchase and sale agreement. The final working capital adjustment, along with additional legal expenses related to the transaction, of $646 was recorded to gain on disposal of discontinued operations, net of income taxes in the three months ended July 31, 2011.

Note 2: Non—GAAP Financial Measures

In addition to disclosing financial results prepared in accordance with Generally Accepted Accounting Principles in the United States (GAAP), we also disclose earnings before interest, taxes, depreciation and amortization, adjusted for accretion, depletion of landfill operating lease obligations, gain on sale of assets, development project charge write-offs, legal settlement charges, bargain purchase gains, asset impairment charges, environmental remediation charges, severance and reorganization charges, as well as expenses from divestiture and financing costs (Adjusted EBITDA) which is a non-GAAP measure. We also disclose earnings before interest, taxes, adjusted for gain on sale of assets, development project charge write-offs, legal settlement charges, bargain purchase gains, asset impairment charges, environmental remediation charges, severance and reorganization charges, as well as expenses from divestiture and financing costs (Adjusted Operating Income) which is a non-GAAP measure. We also disclose Free Cash Flow, which is defined as net cash provided by operating activities, less capital expenditures attributable to growth and maintenance (excluding acquisition related capital), less payments on landfill operating leases, less assets acquired through financing leases, plus proceeds from the sale of property and equipment, plus contributions from non-controlling interest holder, which is a non-GAAP measure. Adjusted EBITDA is reconciled to net income (loss), while Free Cash Flow is reconciled to net cash provided by operating activities.

We present Adjusted EBITDA, Adjusted Operating Income, and Free Cash Flow because we consider them important supplemental measures of our performance and believe they are frequently used by securities analysts, investors and other interested parties in the evaluation of our results. We use these non-GAAP measures to further understand our “core operating performance.” We believe our “core operating performance” represents our on-going performance in the ordinary course of operations. We believe that providing Adjusted EBITDA, Adjusted Operating Income, and Free Cash Flow to investors, in addition to corresponding income statement and cash flow statement measures, affords investors the benefit of viewing our performance using the same financial metrics that our management team uses in making many key decisions and understanding how the core business and our results of operations may look in the future. We further believe that providing this information allows our investors greater transparency and a better understanding of our core financial performance. In addition, the instruments governing our indebtedness use EBITDA (with additional adjustments) to measure our compliance with covenants such as interest coverage, leverage and debt incurrence.

Non-GAAP financial measures are not in accordance with or an alternative for GAAP. Adjusted EBITDA, Adjusted Operating Income, and Free Cash Flow should not be considered in isolation from or as a substitute for financial information presented in accordance with GAAP, and may be different from Adjusted EBITDA, Adjusted Operating Income, or Free Cash Flow presented by other companies.

Following is a reconciliation of Adjusted EBITDA and Adjusted Operating Income to Net Loss:

CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

SUPPLEMENTAL DATA TABLES

(Unaudited)

(In thousands)

Amounts of our total revenues attributable to services provided for the three months ended July 31, 2012 and 2011 are as follows:

CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

SUPPLEMENTAL DATA TABLES

(Unaudited)

(In thousands)

GreenFiber Financial Statistics (1):

(1) Our capital expenditures are broadly defined as pertaining to either growth, maintenance or acquisition activities. Growth capital expenditures are defined as costs related to development of new airspace, permit expansions, and new recycling contracts along with incremental costs of equipment and infrastructure added to further such activities. Growth capital expenditures include the cost of equipment added directly as a result of organic business growth as well as expenditures associated with increasing infrastructure to increase throughput at transfer stations and recycling facilities. Maintenance capital expenditures are defined as landfill cell construction costs not related to expansion airspace, costs for normal permit renewals, and replacement costs for equipment due to age or obsolescence. Acquisition capital expenditures are defined as costs of equipment added directly as a result of new business growth related to an acquisition.