Exhibit 99.1

CASELLA WASTE SYSTEMS, INC. ANNOUNCES FIRST QUARTER FISCAL YEAR 2014 RESULTS; AND REVISES FISCAL YEAR 2014 GUIDANCE UPWARD

RUTLAND, VERMONT (August 28, 2013) — 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 2014, and revised its guidance for its fiscal year 2014.

Highlights for the quarter included:

For the quarter ended July 31, 2013, revenues were $128.6 million, up $10.9 million, or 9.3 percent, from the same quarter last year, with revenue growth mainly driven by higher volumes across all lines-of business, acquisition activity, and higher solid waste collection pricing. Overall solid waste pricing growth of 0.5 percent was primarily driven by residential and commercial pricing growth of 1.9 percent as a percentage of segment revenues.

The company’s net loss attributable to common stockholders was ($0.2) million, or ($0.00) per share for the quarter, compared to net loss of ($8.4) million, or ($0.31) per share for the same quarter last year.

Operating income was $9.7 million for the quarter, up $3.9 million from the same quarter last year. The current quarter includes a $0.1 million severance and reorganization charge related to general realignment activities and by comparison, the quarter ended July 31, 2012 included $0.6 million of expenses related to divestiture and financing costs. Excluding these charges, Adjusted Operating Income* in the current quarter was $9.9 million, up $3.5 million from same quarter last year.

Adjusted EBITDA was $28.7 million for the quarter, up from $24.3 million in the same quarter last year.

“We had a solid first quarter, with results primarily driven by continued execution in key areas of management focus—sourcing incremental landfill volumes; improving collection route profitability; and completing the multi-year Eastern region strategy,” said John W. Casella, chairman and CEO of Casella Waste Systems.

“Our success in the quarter was led by solid performance at our landfills, with tonnages up 175,000 tons year-over-year, excluding the planned declines at the Worcester landfill closure project,” Casella said. “We believe that this improvement is directly attributable to our actions to improve our special waste sales efforts, several new additions to our landfill team, and a tightening disposal market in select markets. We continue to experience these same positive landfill tonnage trends into August.”

“During the quarter, our recycling team did an excellent job leveraging their quality control processes and infrastructure to drive higher volumes and tip fees at our MRFs, offsetting much of the decline in commodity pricing” Casella said. “We do not expect commodity pricing to rebound in the near term; however we do believe that our differentiated platform will continue to drive higher volumes, offsetting the majority of pricing pressure.”

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Fiscal 2014 Outlook

“After a good first quarter and better visibility into the remainder of our fiscal year, we have revised our fiscal year 2014 guidance for revenues and Adjusted EBITDA,” Casella said. “This upward revision is based on a conservative and consistent framework for all assumptions outside of our direct control, such as new landfill volumes or economic growth. We have chosen to leave free cash flow guidance in place this early in the fiscal year.”

The company updated guidance for its fiscal year 2014, which began May 1, 2013, by estimating results in the following ranges:

*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, tax settlement costs, bargain purchase gains, asset impairment charges, environmental remediation charges, severance and reorganization charges, expenses from divestiture, acquisition and financing costs, as well as losses on divestiture (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-offs, legal settlement charges, tax settlement costs, bargain purchase gains, asset impairment charges, environmental remediation charges, severance and reorganization charges, expenses from divestiture, acquisition and financing costs, as well as losses on divestiture (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 holders, which is a non-GAAP measure. Adjusted EBITDA and Adjusted Operating Income are 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.

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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, Chief Financial Officer 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 29, 2013 at 10:00 a.m. ET. Individuals interested in participating in the call should dial (877) 548-9590 or (720) 545-0037 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 28418433) until 11:59 p.m. ET on Thursday, September 5, 2013.

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 increase volumes at our landfills or improve our route profitability; our need to service our indebtedness may limit our ability to invest in our business; 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 not fully recognize the expected financial benefits from the BBI acquisition due to the an inability to recognize operational cost savings, general and administration cost savings, or landfill or recycling facility internalization benefits. 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, 2013.

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

Chief Financial Officer

(802) 772-2239

Media:

Joseph Fusco

Vice President

(802) 772-2247

http://www.casella.com

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CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(Unaudited)

(In thousands, except amounts per share)

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CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED BALANCE SHEETS

(In thousands)

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CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(Unaudited)

(In thousands)

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CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

(In thousands)

Note 1: Divestiture and Discontinued Operations

Maine Energy Divestiture

In the first quarter of fiscal year 2013, we executed a purchase and sale agreement with the City of Biddeford, Maine, pursuant to which we agreed to sell the real property of Maine Energy Recovery Company LP (“Maine Energy”), which is located in our Eastern region, to the City of Biddeford, subject to satisfaction of conditions precedent and closing. We agreed to sell Maine Energy for undiscounted purchase consideration of $6,650, which will be paid to us in equal installments over the next 21 years, subject to the terms of the purchase and sale agreement. The transaction closed in November 2012, and we waived certain conditions precedent not satisfied at that time. In December 2012, we closed the Maine Energy facility and initiated the decommissioning process in accordance with the provisions of the agreement. Following the decommissioning of the Maine Energy facility, it is our responsibility to demolish the facility, at our cost, within twelve months of the closing date and in accordance with the terms of the purchase and sale agreement. We will continue to finalize estimates and obtain additional information regarding the estimated costs associated with the divestiture. Due to the inherent judgments and estimates regarding the remaining costs to fulfill our obligation under the purchase and sale agreement to demolish the facility and remediate the site, recognition of a loss on divestiture, which we do not expect, or a potential gain on divestiture is possible.

As a part of the closure and decommissioning of the Maine Energy facility, we are withdrawing from a multiemployer pension plan to which we have made contributions for the benefit of Maine Energy employees covered under a collective bargaining agreement. We have a potential liability associated with our withdrawal from the multiemployer pension plan based on the value of the plan’s unfunded vested benefits. In accordance with Financial Accounting Standards Board Accounting Standards Codification 715-80, in a situation with unfunded vested benefits, a liability is not recorded by a participating employer as no single employer has an identifiable share of the actuarial obligation of the multiemployer pension plan.

Discontinued Operations

In the fourth quarter of fiscal year 2013, we initiated a plan to dispose of KTI Bio Fuels, Inc. (“Bio Fuels”), a construction and demolition material processing facility located in Lewiston, Maine, and as a result, the assets associated with Bio Fuels were classified as held-for-sale and the results of operations were recorded as loss from discontinued operations. Assets of the disposal group classified as held-for-sale, and now as discontinued operations, include certain inventory along with plant and equipment. In the three months ended July 31, 2013, we executed a purchase and sale agreement with ReEnergy Lewiston LLC (“ReEnergy”), pursuant to which we agreed to sell certain assets of Bio Fuels, which is located in our Eastern region, to ReEnergy. We agreed to sell the Bio Fuels assets for undiscounted purchase consideration of $2,000, which will be paid to us in equal quarterly installments commencing November 1, 2013 and continuing over five years, subject to the terms of the purchase and sale agreement. We recognized a $378 loss on disposal of discontinued operations in the three months ended July 31, 2013 associated with the disposition. Revenues and income (loss) before income taxes attributable to discontinued operations for the three months ended July 31, 2013 and 2012, respectively, are as follows:

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, tax settlement costs, bargain purchase gains, asset impairment charges, environmental remediation charges, severance and reorganization charges, expenses from divestiture, acquisition and financing costs, as well as losses on divestiture (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, tax settlement costs, bargain purchase gains, asset impairment charges, environmental remediation charges, severance and reorganization charges, expenses from divestiture, acquisition and financing costs, as well as losses on divestiture (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 holders, which is a non-GAAP measure. Adjusted EBITDA and Adjusted Operating Income are 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.

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

Following is a reconciliation of Free Cash Flow to Net Cash Provided by Operating Activities:

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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, 2013 and 2012 are as follows:

Components of revenue growth for the three months ended July 31, 2013 compared to the three months ended July 31, 2012 are as follows:

Solid Waste Internalization Rates by Region:

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CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

SUPPLEMENTAL DATA TABLES

(Unaudited)

(In thousands)

GreenFiber Financial Statistics (1):

Components of Growth and Maintenance Capital Expenditures (1):

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CASELLA WASTE SYSTEMS, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(Unaudited)

(In thousands, except amounts per share)

We have included the following restated quarterly condensed consolidated statements of operations, as well as related Adjusted EBITDA and Adjusted Operating Income schedules, to show the impact that discontinued operations treatment for BioFuels had on our results of operations in fiscal year 2013. In addition, the revenue segment data has been restated by quarter to reflect the realigned segments that were adopted effective May 1, 2013.

Condensed consolidated statements of operations by quarter for the fiscal year ended April 30, 2013 are as follows:

Amounts of our total revenues attributable to services provided by quarter for the fiscal year ended April 30, 2013 are as follows:

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Following is a reconciliation of Adjusted EBITDA to Net Loss by quarter for the fiscal year ended April 30, 2013: