Pertambangan Batubara: Pro dan Kontra

Indonesia adalah eksportir batubara terbesar kedua di dunia (setelah Australia, 2006). Batubara yang banyak diekspor adalah batubara jenis sub-bituminus yang dapat merepresentasikan produksi batubara Indonesia. Produksi batubara Indonesia meningkat sebesar 11.1% pada tahun 2003 dan jumlah ekspor meningkat sebesar 18.3% di tahun yang sama. Sebagian besar cadangan batubara Indonesia terdapat di Sumatra bagian selatan. Kualitasnya beragam antara batubara kualitas rendah seperti lignit (59%) dan sub-bituminus (27%) serta batubara kualitas tinggi seperti bituminus dan antrasit (14%).

Sekitar 74% dari batubara Indonesia merupakan hasil penambangan perusahaan swasta. Satu-satunya Badan Usaha Milik Negara (BUMN), PT Tambang Bukit Asam, menghasilkan sekitar 10 Mt (hanya 9% dari total produksi batubara Indonesia pada tahun 2003) dari penambangan terbuka. Bandingkan dengan perusahaan-perusahaan swasta seperti PT Adaro, PT Kaltim Prima Coal, serta PT Arutmin yang dapat memproduksi batubara hingga di atas 10 Mt pada tahun yang sama. Terlihat ironis bukan? Perusahaan penambangan batubara milik negara kalah produksi oleh perusahaan swasta.

Operasi penambangan batubara seringkali dituduh menyebabkan kerusakan lingkungan. Penambangan batubara diperkirakan menyebabkan kerusakan pada kurang lebih 70 ribu hektar tanah. Pada beberapa area, limbah cair dibuang pada sungai terdekat yang pada akhirnya mencemari sumber air warga sekitar. Dampak lingkungan serta permintaan akan kontribusi perusahaan pertambangan yang lebih besar kepada perkembangan masyarakat telah menyebabkan munculnya permintaan akan ditutupnya operasi penambangan batubara. Salah satu hal yang dapat dilakukan untuk mengurangi pengrusakan lingkungan oleh operasi penambangan batubara adalah dengan lebih memperketat regulasi yang berkaitan dengan penambangan batubara, disinilah peran besar pemerintah. Pemerintah merespon permasalahan ini dengan memberikan komitmen bahwa operasi penambangan batubara akan merujuk pada peraturan pemerintah mengenai keselamatan lingkungan. Sebagai contoh, pada tahun 1999 diterbitkan PP no 18 yang mengatur mengenai tata cara pemrosesan limbah berbahaya dan beracun. Peraturan ini mengharuskan perusahaan pertambangan untuk memproses limbah yang dihasilkan hingga mencapai derajat kebersihan yang sangat tinggi dengan standar kemurnian air yang 5 kali lebih ketat dibandingkan Amerika Serikat maupun Kanada. Akan tetapi, penerapan regulasi ini pada akhirnya ditunda karena pemerintah mengevaluasi ulang kemampuan teknologi yang dimiliki oleh perusahaan pertambangan di Indonesia dan ternyata dibutuhkan penyesuaian. Belum lagi adanya penambangan batubara ilegal. Para penambang ilegal mengabaikan ketentuan yang berkaitan dengan lingkungan dan keselamatan serta menjual batubara dengan harga yang lebih rendah. Pemerintah diharapkan dapat mengambil sikap dan menuntut para penambang ilegal ini.

Pemerintah sendiri memiliki ketertarikan yang besar dalam mengembangkan teknologi pemanfaatan batubara untuk mengurangi dampak lingkungan yang ditimbulkan oleh batubara. Usaha untuk mengembangkan Clean Coal Technology (CCT) telah memasukkan kerjasama dengan pihak asing untuk mempelajari efek-efek yang mungkin muncul dari penggunaan batubara dan untuk mencari cara baru agar pembangkit listrik yang berbasis pembakaran batubara dapat memenuhi ketentuan lingkungandari segi emisi. Ini suatu itikad baik yang ditunjukkan oleh pemerintah mengingat permasalahan yang menyangkut emisi yang dihasilkan oleh batubara dapat mengurangi visibilitas digunakannya batubara sebagai sumber energi.

Masalah sumber energi pun sedang menjadi fokus utama pemerintah berkaitan dengan naiknya harga minyak bumi. Pada dasarnya, cadangan batubara Indonesia memang jauh lebih besar dibandingkan dengan cadangan minyak bumi maupun gas alam sehingga pemerintah kini mulai melihat batubara sebagai sumber energi alternatif yang murah. Batubara selama ini telah digunakan sebagai bahan bakar pada pabrik semen dan pabrik baja, apa salahnya jika batubara digunakan untuk membangkitkan listrik? Apabila hal ini dapat dilakukan, subsidi pemerintah untuk BBM dapat berkurang (saat ini subsidi memang tidak mencukupi akibat kenaikan harga minyak bumi dan peningkatan konsumsi BBM). Dalam 3 tahun mendatang diharapkan telah berdiri PLTU Batubara dengan kapasitas daya listrik yang dapat dihasilkan sebesar 10000 MW.

Tampaknya untuk mewujudkan hal itu, pemerintah dan industri pertambangan batubara harus bekerja lebih keras. Dengan perkiraan heating value batubara Indonesia yang berada pada kisaran 5000 sampai 7000 kal/kg, berapa banyak batubara yang harus diproduksi untuk menghasilkan listrik 10000 MW? Apakah perusahaan pertambangan di Indonesia dapat menemukan cara untuk menambang batubara tanpa menimbulkan kerusakan lingkungan?

Tampaknya jawaban pertanyaan di atas adalah TIDAK. Atau mungkin BELUM. Tanah yang dikeruk, polusi yang disebabkannya, serta bekas yang ditinggalkannya masih akan menjadi masalah lingkungan di kemudian hari. Mungkin saat ini yang bisa dilakukan adalah meningkatkan kinerja unit-unit penanganan limbah sekaligus melakukan transfer teknologi terkait dengan keterbatasan yang kita miliki dalam teknologi penambangan, mengurangi penambang-penambang ilegal, dan secara bertahap melakukan rehabilitasi lahan pertambangan yang telah ditinggalkan. MENGAPA? Karena lebih tidak mungkin menghentikan penambangan batubara yang saat ini diharapkan bisa menjadi penyelamat bagi krisis energi yang melanda Indonesia.

by Ratih Asthary

Batu Hijau Copper-Gold Mine, Indonesia

Batu Hijau copper-gold mine is located on the Indonesian island of Sumbawa in the province of West Nusa Tenggara, 1,530km east of Jakarta. The Contract of Work for the project is held by PT Newmont Nusa Tenggara (PTNNT), a company owned by Newmont Indonesia Ltd (USA, 45%); Nusa Tenggara Mining Corporation (Japan, 35%) and PT Pukuafu Indah (Indonesia, 20%). Newmont is the project operator and has a 52.875% equity stake. Construction of the mine and its associated infrastructure was completed in 1999, after PTNNT had spent ten years exploring the resource, with commercial production beginning in 2000. The operation continues to be one of Newmont’s lowest cost assets. In 2005, copper sales fell 16.2% to 259,780t (2004= 310,000t) at an applicable cost of $0.53/lb and an average realised price before TRCs of $1.45/lb. However, consolidated gold sales rose to 720,500oz at applicable costs of $152/oz, as compared with 715,000oz in 2004. Power for the project is supplied by a 120MW coal-fired plant supported by nine diesel generators. GEOLOGY AND RESOURCES "During 2005, Batu Hijau produced and shipped 1.1Mt of copper concentrate containing 325,500t of copper and 719,000oz of gold." Bata Hijau is a major gold-rich porphyry copper deposit typical of the islands of southeast Asia. These gold-rich porphyries are overwhelmingly hosted by composite stocks of diorite to quartz-diorite and, to a much lesser degree, more felsic compositions such as tonalite and monzogranite. The deposits tend to be characterised by a strong correlation between the distribution of copper sulphides (chalcopyrite and bornite) and gold as the native metal in addition to having a notably higher magnetite content. Gold typically occurs as minute (<10-15> As of the end of 2005, Batu Hijau had an ore reserve containing 2.77Mt copper with 0.69g/t gold. At current production rates, mining should continue until 2025. MINING AND MILLING Batu Hijau is an open-pit mine. Ore is transported to the primary crushers using P&H 4100 electric mining shovels and a fleet of 220t-capacity Caterpillar 793C mechanical-drive haul trucks. The mine typically handles around 600,000t/d of ore and waste, the ore grading an average 0.49% copper and 0.39g/t gold. Following primary crushing, the ore is transported to the concentrator by an overland conveyor, 1.8m wide and 6.8km long. The concentrator circuit consists of two-train SAG and ball mills, followed by primary and scavenger flotation cells, vertical regrind mills and cleaning flotation cells to produce a copper-gold concentrate grading 32% copper and 19.9g/t gold. Counter-current decantation thickeners are used to dewater the concentrate to a slurry, which is pipelined 17.6km from the plant to the port at Benete. Here it is dewatered further, then stocked in an 80,000t-capacity storage area prior to shipment by sea. PRODUCTION During 2005, Batu Hijau produced and shipped 1.1Mt of copper concentrate containing 325,500t of copper and 719,000oz of gold. TAILINGS DEPOSITION The tailings from the operation flow by gravity from the process plant to the ocean where they are deposited 3km from the coast at a depth of about 108m. From there, the tailings, which are non-toxic and non-hazardous, migrate towards the Java Trench and are ultimately deposited at depths in excess of 4,000m. ENVIRONMENT There are considerable environmental challenges at Bata Hijau, including steep terrain and widely dispersed facilities stretching over 40km. The site has a tropical monsoonal climate with high rainfall, and an extended arid season with almost no rainfall. Other environmental considerations include significant seismic activity, with the associated risk of tsunamis, and acid rock drainage, not to mention the existence on site of an endangered species, the yellow-crested cockatoo. Considerable environmental controls are in place, and Newmont reported the operation improved its ‘five-star’ environment rating to four stars in 2005. From : Mining-Technology.com		Batu Hijau is located on the Indonesian island of Sumbawa. Minahasa, also shown on the map, is another Newmont operation.
		Aerial view of the Batu Hijau open pit.
		Blasting in the open pit.
		Haul trucks moving ore at Batu Hijau.
		Aerial view of the concentrator at Batu Hijau.
		The mine's dedicated port facilities at Benete Bay.
		Reclamation reseeding through geotextiles used to prevent erosion of the ground surface by the weather.

Coal Mountain Coal Mine, British Columbia, Canada

Situated 30km south east of Sparwood, in south-eastern British Columbia, the Coal Mountain metallurgical/thermal coal mine produces metallurgical and thermal products for international steelmakers and other industries. Formerly owned by Esso Resources Canada Ltd, and operated by its Byron Creek Collieries subsidiary, Coal Mountain was acquired by Fording Coal in 1994. In 2003, ownership of Coal Mountain was transferred to the Elk Valley Coal Partnership, now 60% owned by Fording Canadian Coal Trust and 40% by the major Canadian mining company, Teck Cominco. Elk Valley Coal is the world's second-largest supplier of metallurgical coal, with an output in 2004 of a near-capacity 24.9Mt. "Enhancements to the processing plant have improved plant yield while allowing greater flexibility in controlling coal quality." After purchasing the mine, Fording embarked on a major mobilisation and upgrading programme that included preproduction stripping, exploration, the purchase of larger, more efficient mining equipment, and significant modifications to the processing plant. Coal Mountain now has a mine capacity of 2.7Mt/y while its washing plant can handle up to 3.5Mt/y of run-of-mine coal. Its actual output in 2006 was 2.0Mt, down from 2.3Mt in 2005 and 2.5Mt in 2004. GEOLOGY As with the neighbouring Elk River coalfield to the north, coal resources in the Crowsnest district are hosted in rocks of the jurassic Kootenay formation. The strata have been extensively folded and faulted, a factor that has helped increase the apparent thickness of seams in some areas. Resources at Coal Mountain are generally of mid-volatile bituminous rank. As of end-2006, the mine's proven reserve totalled over 26Mt of clean coal, with a further 111Mt of measured and indicated resources. These are contained within three coal horizons, the largest being the Mammoth seam, which varies from 1m to 200m in thickness across the property. Reserves are adequate to support mining for at least 13 more years at the production rate achieved in 2006. MINE AND PROCESS PLANT OPERATION Open-pit mining is used at Coal Mountain. Overburden stripping and coal production rely on a shovel-and-truck operation. The principal excavators are two O&K RH200 hydraulic shovels with 21 and 26m³-capacity buckets and a LeTourneau 21m³ wheel loader. These are used to load overburden and interburden into the operations' fleet of 136t- and 218t-capacity haul trucks. Enhancements to the processing plant, including the addition of the most up-to-date process control technology, have improved plant yield while allowing greater flexibility in controlling coal quality. In common with Elk Valley Coal's other operations in British Columbia and Alberta, Coal Mountain's washing plant has an automated sampling system on its product stream. Online neutron-activated ash and moisture analysers are used to provide data that permits the plant's operators to monitor and tightly control product quality. PRODUCT TRANSPORTATION The loading process at all of Elk Valley Coal's operations is monitored by a central computer which controls the automated system. Rail cars can be loaded to within 0.5% of their capacity to prevent over- or under-loading. "Elk Valley Coal is the world's second-largest supplier of metallurgical coal." Access to its parent company, Canadian Pacific's, rail system and the export port at Roberts Bank provides Elk Valley Coal with one of the lowest cost transport systems in the world, on a per-tonne-per-kilometre basis. CP Rail uses 112-wagon unit trains to handle Fording’s output, making a round trip over the 1,175km-long journey from the south-eastern BC mines to the coast in around 85 hours. Roberts Bank, operated by Westshore Terminals, has an annual throughput capacity exceeding 22Mt and is the largest coal-loading port on the west coast of North America. Elk Valley Coal has over 600,000t of storage capacity at Roberts Bank, where the loadout can accommodate bulk carriers in excess of 250,000dwt. Elk Valley Coal also ships coal east by rail to Thunder Bay terminals at the port of Thunder Bay, Ontario, while direct rail links to the central and eastern USA provide further access to important markets for the company. COAL QUALITY Typical quality parameters for Coal Mountain products are: Mid-volatile PCI coal Mid-volatile steam coal Ash (%) 10.0 – 11.5 15.0 – 17.0 Volatile matter (%) 21.0 – 23.0 21.0 – 23.0 Sulphur (%) 0.3 – 0.4 0.3 – 0.5 Heating value (MJ/kg) 29.3 – 31.0 26.0 – 28.0 From : Mining-Technology.com		Location of Coal Mountain.
		Landscape of Coal Mountain.
		Typical cross-section at Coal Mountain operations.
		Coal Mountain processing plant.
		Trucks and loader.
		Canadian Pacific Railway Co’s 112-car unit trains to transport its products to tidewater.
		Westshore terminals, with an annual throughput capacity exceeding 22Mt.

Crandall Canyon Crandall Canyon , USA

At the end of August 2007, with all efforts having failed to locate the miners missing in the Crandall Canyon mine for more than three weeks – and presumed dead – the US Department of Labor announced an independent investigation to look into the handling of the disaster. The coal mine is located in the north-west of Emery County, 35 miles south-east of Fairview and 15 miles west north-west of Huntington, just off Utah State Route 31 and surrounded by the Manti-LaSal National Forest. The mine permit area extends to over 5,000 acres and occupies fee land as well as federal and state leases, with surface operations being carried out on around ten acres of disturbed land within the forest. The co-owners of the mine are the Intermountain Power Agency (IPA) and UtahAmerican Energy (formerly Andalex Resources) a subsidiary of the Murray Energy Corporation, with Genwal Resources – the operating division of UtahAmerican – responsible for running it. GEOLOGY AND RESERVES The mine is in the Wasatch Plateau coal field, which is characterised by fine to medium grain late Cretaceous grey sandstone, inter-bedded with subordinate light and dark grey carbonaceous shales and coal, with continental and transitional sediments. Further marine sediments lie below the main deposits. "Three major fault zones have been defined within the coal field, running in a north-south direction." Three major fault zones have been defined within this coal field, running in a north-south direction – products of a high angle block fault with extensive minor fracturing within the graben. The trends of these faults have a complex pattern, which cause difficulties for mining efforts in the affected areas. The South Crandall Hiawatha seam, for example, holds up to 12.7 million tons of potentially mineable reserves, but the difficult geology and the thin lenticular coal seam makes getting it out very difficult. The mine produced 1.7 million tons in 2006 and has an estimated recoverable reserve of 13 million tons. MINING Mining began at the Crandall Canyon site in November 1939 and continued using a room and pillar method until September 1955. In 1983, the Genwal Coal Company resumed mining operations, producing an annual total of between 90–210,000t of coal, and in 1989, NEICO purchased the mine. IPA bought a 50% interest the following year. A continuous haulage system was incorporated into the room and pillar method in 1991, which enabled production to rise to 1–1.5 million tons per year. The mine was transferred to Genwal Resources in March 1995 and a longwall system was subsequently installed, which effectively doubled the mine’s capacity. A second new longwall was put in place two years later and a new loadout facility was built at the mine to handle the increased capacity. In 2004, a new low-profile longwall machine – able to cut coal in a seam little more than 5ft (1.5m) thick – was installed. THE COLLAPSE On Monday 6th August 2007, the mine collapsed, trapping six miners 1,500ft (460m) underground, some 3.5 miles (5.5km) from the entrance. The shock waves registered 3.9 to 4.0 by seismographic stations in Utah and Nevada, leading to an initial belief that the collapse had been caused by an earthquake. However, it appears that the collapse happened while miners were engaged in retreat mining – the final stage of a room and pillar operation when the pillars of coal used to hold up an area of the roof are intentionally removed to allow the last of the coal to be recovered. "On Monday 6th August 2007, the mine collapsed, trapping six miners 1,500ft underground" It is an established method of mining, but it is a particularly hazardous one. According to studies by the US National Institutes of Occupational Safety and Health, retreat mining is one of the biggest causes of mine-roof-collapse deaths. Although it accounts for only around 10% of underground coal production, a coal miner is more than three times as likely to be fatally injured by a roof collapse when engaged in this type of mining than any other. Rescue teams were dispatched immediately and began the work of assessing the damage to the mine structure and clearing rubble. On the 9th August, a 2.5in (6cm) hole was bored 1,800ft (549m) towards where the miners were assumed to be trapped. A microphone was lowered and though it did not register any activity, initial samples suggested the air was breathable. Unfortunately, it was later to be established that it was not. A second and larger hole was made at another possible location and a camera used – revealing mining equipment but no miners. A third bore hole was created near to the ventilation area, followed by a fourth targeted towards noises that geophones briefly detected coming from the mine for five minutes on the evening of 15th August. By noon the following day – now 11 days after the collapse – underground rescue teams had only been able to advance around halfway through the rubble; at 6.30 that evening, one of the tunnel walls burst, collapsing the mine again killing three of the rescuers and injuring six others. The remaining rescue teams were pulled from the mine. The fifth, sixth and eventually – at the end of August – seventh bore holes were also all to fail to find either signs of life, or the bodies of the missing miners. Inevitably there has been much criticism voiced, especially of the mine’s owners for ignoring prior safety warnings and the US Mine Safety and Health Administration both for its handling of events and for allowing retreat mining in the first place. "Retreat mining is one of the biggest causes of mine-roof-collapse deaths." With the members of the independent investigation panel – Ernest C. Teaster Jr. and Joseph W. Pavlovich – named at the beginning of September 2007, the process of working out exactly what went so tragically wrong can get underway. Their enquiry is expected to take around six months to come to its conclusions. THE FUTURE The future of the mine seems uncertain and the Utah mining community remains divided over the issue of re-opening it. Murray Energy vice president Rob Moore is reported to have said that the company expected to resume operations "at some point" to access the recoverable coal in other parts of the mine. However, Robert E. Murray, the CEO of Murray Energy, has stated that he has filed the necessary paperwork with federal regulators to permanently close and seal the Crandall Canyon mine. Even before the disaster, although further federal leases were to extend the useful life of the mine and new access ways planned on the south side, the owners had made it clear to the state of Utah that it was their intention that the mine would close in 2008. From : Mining-Technology.com		Satellite view of the Crandall Canyon mine site, just off Utah State Route 31 in the Manti-LaSal National Forest.
		Longwall underground coal production; this technique played a major part in boosting the mine’s production.
		Map showing the extent of the mine.
		A high resolution dual lens camera system waiting to be lowered into an 1,868ft shaft as part of the rescue effort.
		Diagram detailing the boreholes drilled during the rescue attempt.