Jump to content
Main menu
Main menu
move to sidebar
hide
Navigation
Main page
Recent changes
Random page
Help about MediaWiki
Special pages
Niidae Wiki
Search
Search
Appearance
Create account
Log in
Personal tools
Create account
Log in
Pages for logged out editors
learn more
Contributions
Talk
Editing
Peat
(section)
Page
Discussion
English
Read
Edit
View history
Tools
Tools
move to sidebar
hide
Actions
Read
Edit
View history
General
What links here
Related changes
Page information
Appearance
move to sidebar
hide
Warning:
You are not logged in. Your IP address will be publicly visible if you make any edits. If you
log in
or
create an account
, your edits will be attributed to your username, along with other benefits.
Anti-spam check. Do
not
fill this in!
==Characteristics and uses by nation== ===Latvia=== [[File:Ķemeru purva laipa.jpg|thumb|upright|Ķemeri bog at sunset]] Latvia has been the biggest exporter of peat in the world by volume, providing more than 19.9% of the world's volume, followed only by [[Canada]] with 13% in 2022.<ref>{{Cite web |title=What will be the future of peat? |url=https://www.db.lv/zinas/kad-zalais-kurss-nomaldas-no-kursa-512732 |website=db.lv }}</ref> In 2020, Latvia exported 1.97 million tons of peat, followed by [[Germany]] with 1.5 and [[Canada]] with 1.42 million tons.<ref name="investinlatvia">{{Cite web |title=Latvia is the largest exporter of peat in the world |url=https://investinlatvia.org/en/news/latvia-is-the-largest-exporter-of-peat-in-the-world |website=investinlatvia.org}}</ref> Nevertheless, although first in the world by volume, in monetary terms, Latvian comes second in the world behind [[Canada]]. As an example, Latvia's income from exports was US$237 million.<ref name="investinlatvia"/> Latvia's peat deposits have been estimated to equal 1.7 billion tons.<ref>{{Cite web |title=What is peat and what is a peat deposit? |url=http://www.latvijaskudra.lv/en/Interesting_information/interesanta_informacija/ |website=latvijaskudra.lv }}</ref> Latvia, as [[Finland]] due its climate has several peat bogs, which account for 9.9% of the country's territory.<ref>{{Cite web |title=Peat in Latvia |url=https://videscentrs.lvgmc.lv/lapas/peat |website=videscentrs.lvgmc.lv }}{{Dead link|date=April 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> More than two thirds of the licensed areas for peat extraction are state-owned; 55% belong to the state whilst 23% belong to the municipalities<ref name="latvijaskudra">{{Cite web |title=Peat in Latvia |url=http://www.latvijaskudra.lv/en/Interesting_information/interesanta_informacija/ |website=latvijaskudra.lv }}</ref> Bogs in Latvia are considered important habitats due to their ecological values, and up to 128,000 hectares, or 40% of the areas in the territory, are protected by environmental laws.<ref name="latvijaskudra"/> The most famous national parks and reserves are the [[Ķemeri National Park]], [[Cenas tīrelis]] and [[Teiči Nature Reserve]]. ===Finland=== {{Update section|date=January 2022}}[[File:Toppila power plant.JPG|thumb|upright|The [[Toppila Power Station]], a peat-fired facility in [[Oulu]], Finland]] The climate, geography and environment of [[Finland]] favours bog and peat bog formation. Thus, peat is available in considerable quantities. It is burned to produce [[Peat energy in Finland|heat and electricity]]. Peat provides around 4% of Finland's annual energy production.<ref>{{Cite web |title=Statistics Finland – Energy supply and consumption |url=https://www.stat.fi/til/ehk/2021/01/ehk_2021_01_2021-06-30_tie_001_en.html |website=stat.fi }}</ref> Also, agricultural and forestry-drained peat bogs actively release more CO<sub>2</sub> annually than is released in peat energy production in Finland. The average regrowth rate of a single peat bog, however, is indeed slow, from 1,000 up to 5,000 years. Furthermore, it is a common practice to forest used peat bogs instead of giving them a chance to renew. This leads to lower levels of CO<sub>2</sub> storage than the original peat bog. At 106 g CO<sub>2</sub>/[[Joule|MJ]],<ref name="imcg.net">[http://www.imcg.net/imcgnl/nl0702/kap05.htm The CO<sub>2</sub> emission factor of peat fuel] {{webarchive|url=https://web.archive.org/web/20100707134451/http://www.imcg.net/imcgnl/nl0702/kap05.htm|date=2010-07-07}}. Imcg.net. accessed on 2011-05-09.</ref> the carbon dioxide emissions of peat are higher than those of coal (at 94.6 g CO<sub>2</sub>/MJ) and [[natural gas]] (at 56.1). According to one study, increasing the average amount of wood in the fuel mixture from the current 2.6% to 12.5% would take the emissions down to 93 g CO<sub>2</sub>/MJ. That said, little effort is being made to achieve this.<ref>{{Cite web |title=VTT 2004: Wood in peat fuel – impact on the reporting of greenhouse gas emissions according to IPCC guidelines |url=http://virtual.vtt.fi/inf/pdf/workingpapers/2004/W12.pdf |website=virtual.vtt.fi |date= |url-status=dead |archive-url=https://web.archive.org/web/20070927010519/http://virtual.vtt.fi/inf/pdf/workingpapers/2004/W12.pdf |archive-date=2007-09-27 |access-date=2006-12-20}}</ref> The International Mire Conservation Group (IMCG) in 2006 urged the local and national governments of Finland to protect and conserve the remaining pristine peatland ecosystems. This includes the cessation of drainage and peat extraction in intact mire sites and the abandoning of current and planned groundwater extraction that may affect these sites. A proposal for a Finnish peatland management strategy was presented to the government in 2011, after a lengthy consultation phase.<ref>{{cite journal |last1=Salomaa |first1=Anne |last2=Paloniemi |first2=Riikka |last3=Ekroos |first3=Eri |date=2018 |title=The case of conflicting Finnish peatland management – Skewed representation of nature, participation and policy instruments |journal=[[Journal of Environmental Economics and Management]] |volume=223 |pages=694–702 |doi=10.1016/j.jenvman.2018.06.048 |pmid=29975897 |doi-access=free|bibcode=2018JEnvM.223..694S }}</ref> === Sweden === [[File:Saltmyrans torvtäkt 13.jpg|thumb|Tractor used for peat cutting in Saltmyran, [[Arvidsjaur Municipality|Arvidsjaur]], Sweden]] About 15% of the land in [[Sweden]] is covered by peatlands.<ref name="sgu.se">{{Cite web |title=Peat |url=https://www.sgu.se/en/physical-planning/energy/peat/ |access-date=2023-10-27 |website=sgu.se |language=en}}</ref> Whilst nowadays the main use of such soils is for [[forestry]], peat-rich lands have historically been exploited to produce energy, agricultural land and horticultural substrates.<ref name="sgu.se"/> The most common method to extract peat during the 19th and 20th centuries was [[Peat Cutting Monday|peat cutting]], a process where the land is cleared of forest and subsequently drained.<ref name="sgu.se"/> Peat cores are then extracted under dry weather conditions and stored on stacks to let the residual moisture evaporate.<ref name="sgu.se"/> Today, clear-cutting for [[horticultural]] peat (of which Sweden is an important producer in Europe) is limited to some areas of Sweden and strictly regulated by the [https://www.naturvardsverket.se/en/laws-and-regulations/the-swedish-environmental-code/ Swedish Environmental Code] to prevent that significant groundwater storages and carbon sinks areas are altered and compromised by human activities.<ref name="sgu.se"/> At the same time, restoration of drained peatlands through rewetting is urged by national and international policies to exploit the peat-rich soil properties in mitigating climate change effects.<ref>{{Cite web |title=Därför är våtmarker viktiga |url=https://www.naturvardsverket.se/amnesomraden/vatmark/varfor-ar-vatmarker-sa-viktiga/ |access-date=2023-10-27 |website=naturvardsverket.se |language=sv}}</ref> ===Ireland=== [[File:BordnaMona 2930.jpg|thumb|left|Industrial-milled peat production in a section of the [[Bog of Allen]] in the Irish Midlands: The 'turf' in the foreground is machine-produced for domestic use.{{Citation needed|date=January 2022}}]] In [[Republic of Ireland|Ireland]], a state-owned company called {{lang|ga|[[Bord na Móna]]}} was responsible for managing peat extraction. It processed the extracted peat into milled peat used in power stations and sold processed peat fuel in the form of peat [[briquette]]s, which is used for domestic heating. These are oblong bars of densely compressed, dried, and shredded peat. [[Peat moss]] is a manufactured product for garden cultivation. Turf (dried-out peat [[sod]]s) is also commonly used in rural areas.{{Citation needed|date=June 2021}} In January 2021, Bord na Móna announced that it had ceased all peat harvesting and cutting operations and would move its business to a climate solutions company.<ref>{{cite news |last=O'Doherty |first=Caroline |date=14 January 2021 |title=Bord na Móna confirms it has ended peat harvesting for good |work=Independent |url=https://www.independent.ie/news/bord-na-mona-confirms-it-has-ended-peat-harvesting-for-good-39970397.html |access-date=15 January 2021}}</ref> In 2022, selling peat for burning was prohibited, but some people are still allowed to cut and burn it.<ref>{{Cite web |last=Dublin |first=Barry Hartigan in |title=A burning issue for Ireland as the sale of peat is outlawed |url=https://www.sundaypost.com/fp/a-burning-issue-for-ireland-as-the-sale-of-peat-is-outlawedthis-is-a-fuel-poverty-issue-as-there-are-around-100000-homes-that-burn-turf-and-who-dont-have-a-choice/ |access-date=2022-09-01 |website=The Sunday Post |date=7 August 2022 |language=en-US}}</ref> ===Russia=== [[File:Shatura steam power plant (2010).jpg|thumb|[[Shatura Power Station]]. [[Russia]] has the largest [[List of peat power stations|peat power]] capacity in the world.|left]][[File:Peat Briquette Factory.jpg|thumb|The [[Kerzhenets peat narrow gauge railway|Bor Peat Briquette Factory]], [[Russia]]]]{{Update section|date=August 2020}} The use of peat for energy production was prominent in the [[Soviet Union]], especially in 1965. In 1929, over 40% of the Soviet Union's electric energy came from peat, which dropped to 1% by 1980. In the 1960s, larger sections of swamps and bogs in Western Russia were drained for agricultural and mining purposes.<ref name="wildfire">{{cite web |author=Serghey Stelmakovich |title=Russia institutes peat fire prevention program |url=http://wildfiremag.com/tactics/russia_institutes_peat/ |url-status=dead |archive-url=https://web.archive.org/web/20100618114909/http://wildfiremag.com/tactics/russia_institutes_peat/ |archive-date=June 18, 2010 |access-date=August 9, 2010}}</ref> ===Netherlands=== [[File: 500vc ex leg copy.jpg|thumb|left|Peat covered area (brown) 2,500 years ago in the Netherlands]]Two-and-a-half thousand years ago, the area now named the [[Netherlands]] was largely covered with peat. Drainage, causing compaction and oxidation and excavation have reduced peatlands (>{{cvt|40|cm|disp=sqbr}} peat) to about {{cvt|2733|km2}}<ref>Joosten, Hans; Tanneberger, Franziska; Moen, Asbjørn. 2017. ''Mires and peatlands of Europe''. Schweizerbart Science Publishers, Stuttgart, Germany. 780 p. Chapter "Netherlands".{{ISBN?}}</ref> or 10% of the land area, mostly used as meadows. Drainage and excavation have lowered the surface of the peatlands. In the west of the country, dikes and mills were built, creating [[polder]]s so that dwelling and economic activities could [[Flood control in the Netherlands|continue]] below sea level, the [[Achtermeer|first polder]] probably in 1533<ref>Reh, W., Steenbergen, C., Aten, D. 2007. ''Sea of Land, The polder as an experimental atlas of Dutch landscape architecture''. 344 pp, Uitgeverij Architectura & Natura. {{ISBN|978-9071123962}}</ref> and the last one in [[Flevopolder|1968]]. Peat harvesting could continue in suitable locations as the lower layers below the current sea level are exposed. This peat was deposited before the sea level rise in the [[Holocene]]. As a result, approximately 26% of the area<ref>{{cite journal |last=Schiermeier |first=Quirin |year=2010 |title=Few fishy facts found in climate report |journal=Nature |volume=466 |issue=170 |page=170 |doi=10.1038/466170a |pmid=20613812 |doi-access=free}}</ref> and 21% of the population<ref>"Milieurekeningen 2008" (PDF). Centraal Bureau voor de Statistiek. Accessed 4 February 2010.</ref> of the Netherlands are presently below sea level. The deepest point is in the [[Zuidplaspolder]], {{cvt|6.76|m}} [[Amsterdam Ordnance Datum|below average sea level]]. [[File:The Netherlands compared to sealevel.png|thumb|right|The Netherlands compared to sea level]] In 2020, the Netherlands imported 2,156 million kg of peat (5.39 million m<sup>3</sup> [400 kg/m<sup>3</sup> dry peat]<ref>{{Cite web |title=Common substances, materials, foods and gravels |url=https://www.aqua-calc.com/page/density-table |website=aqua-calc.com}}</ref>): 44.5% from Germany (2020), 9.5% from Estonia (2018), 9.2% from Latvia (2020), 7.2% from Ireland (2018), 8.0% from Sweden (2019), 6.5% from Lithuania (2020), 5.1% from Belgium (2019) and 1.7% from Denmark (2019); 1.35 million kg was exported.<ref>CBS (opendata.cbs.nl), [https://opendata.cbs.nl/statline/#/CBS/nl/dataset/81268ned/table?dl=2378F Goederensoorten naar land; minerale brandstoffen en chemie] (''tr. "Goods by country; mineral fuels and chemistry")''</ref> Most is used in gardening and [[greenhouse]] [[horticulture]]. Since the Netherlands did not have many trees to use as firewood or charcoal, one use the Dutch made of the available peat was to fire kilns to make pottery.<ref>Prins, Marcel & Steenhuis, Peter Henk, "Hidden," Arthur A. Levine Books, New York, 2011, p. 205.</ref> During World War II, the Dutch Resistance came up with an unusual use for peat. Since peat was so available in the fields, resistance fighters sometimes stacked peat into human-sized piles and used the piles for target practice.<ref>Ibid, p. 204.</ref> ===Estonia=== After [[oil shale in Estonia]], peat is the second-most-mined natural resource.<ref>{{Cite web |title=Peat |url=https://www.turbaliit.ee/en/peat/ |access-date=2022-09-01 |website=Turbaliit |language=en-US}}</ref> The peat production sector has a yearly revenue of around €100 million and it is mostly export-oriented.{{Citation needed|date=September 2022}} Peat is extracted from around {{Convert|14|ha}}.<ref>[https://www.err.ee/1082339/ministeerium-seisvad-turbamaardlad-on-moistlik-taas-kasutusele-votta "Ministeerium: seisvad turbamaardlad on mõistlik taas kasutusele võtta"] ERR, 25 April 2020 (in Estonian)</ref> ===India=== ====Sikkim==== The mountains of the Himalayas and Tibetan Plateau contain pockets of high-altitude wetlands.<ref name="oneill_khecheopalri">{{cite journal |last=O'Neill |first=Alexander |display-authors=etal |date=25 February 2020 |title=Establishing Ecological Baselines Around a Temperate Himalayan Peatland |journal=Wetlands Ecology & Management |volume=28 |issue=2 |pages=375–388 |doi=10.1007/s11273-020-09710-7 |bibcode=2020WetEM..28..375O |s2cid=211081106}}</ref> [[Khecheopalri]] is one of the [[Sikkim]]'s most famous and diverse peatlands in the eastern Indian territory of Sikkim, which includes 682 species representing five kingdoms, 196 families and 453 genera.<ref name="O'Neill_2019">{{cite journal |last=O'Neill |first=A. R. |date=2019 |title=Evaluating high-altitude Ramsar wetlands in the Sikkim Eastern Himalayas |journal=Global Ecology and Conservation |volume=20 |issue=e00715 |page=19 |doi=10.1016/j.gecco.2019.e00715 |doi-access=free}}</ref> ===United Kingdom=== ====England==== England has around 1 million acres of peatland. Peatlands in England store 584m tonnes of carbon in total but emit around 11 million tonnes of {{CO2}} every year due to degradation and draining. In 2021 only 124 people owned 60% of England's peatland.<ref>{{Cite web |date=2021-11-15 |title=Just 124 people own most of England's deep peat – its largest carbon store |url=https://www.theguardian.com/environment/2021/nov/15/just-124-people-own-most-of-england-deep-peat-its-largest-carbon-store-aoe |access-date=2021-11-15 |website=The Guardian |language=en}}</ref> The [[Peat extraction on the Somerset Levels|extraction of peat]] from the [[Somerset Levels]] began during the Roman times and has been carried out since the Levels were first drained.<ref>{{cite web |date=September 2009 |title=Somerset Peat Paper – Issues consultation for the Minerals Core Strategy |url=http://www.somerset.gov.uk/irj/go/km/docs/CouncilDocuments/SCC/Documents/Environment/Minerals%20and%20waste/Mineral%20consultation%20papers/Peat%20Extraction%20Paper.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120310135710/http://www.somerset.gov.uk/irj/go/km/docs/CouncilDocuments/SCC/Documents/Environment/Minerals%20and%20waste/Mineral%20consultation%20papers/Peat%20Extraction%20Paper.pdf |archive-date=10 March 2012 |access-date=30 November 2011 |publisher=[[Somerset County Council]] |page=7}}</ref> On [[Dartmoor]], there were several commercial distillation plants formed and run by the British Patent Naphtha Company in 1844. These produced [[naphtha]] on a commercial scale from the high-quality local peat.<ref>[http://www.legendarydartmoor.co.uk/peat_moor.htm Dartmoor Peat] {{Webarchive|url=https://web.archive.org/web/20120405153646/http://www.legendarydartmoor.co.uk/peat_moor.htm |date=2012-04-05 }}, Dartmoor history</ref> [[Fenn's, Whixall and Bettisfield Mosses]] is an element of a post-[[Last glacial period|Ice Age]] peat bog that straddles the England–[[Wales]] border and contains many rare plant and animal species due to the acidic environment created by the peat.<ref>{{cite web |title=Mawndiroedd Fenn's, Whixall a Bettisfield |url=http://www.ccgc.gov.uk/landscape--wildlife/protecting-our-landscape/special-landscapes--sites/protected-landscape/national-nature-reserves/fenns-whixall-and-bettisfiel.aspx |url-status=dead |archive-url=https://web.archive.org/web/20131029202832/http://www.ccgc.gov.uk/landscape--wildlife/protecting-our-landscape/special-landscapes--sites/protected-landscape/national-nature-reserves/fenns-whixall-and-bettisfiel.aspx |archive-date=2013-10-29 |access-date=2013-10-27}}</ref> Only lightly hand-dug, it is now a [[national nature reserve (United Kingdom)|national nature reserve]] and is being restored to its natural condition. The industrial extraction of peat occurred at the [[Thorne and Hatfield Moors|Thorne Moor]] site, outside [[Doncaster]] near the village of [[Hatfield, South Yorkshire|Hatfield]]. Government policy incentivised commercial removal to peat for agricultural use. This caused much destruction of the area during the 1980s. The removal of the peat resulted in later flooding further downstream at [[Goole]] due to the loss of water retaining peatlands.<ref>Walker, M. D. Sphagnum. Sicklebrook Press. {{ISBN|978-0-359-41313-3}}</ref> Recently regeneration of peatland has occurred as part of the Thorne Moors project, and at [[Fleet Moss]], organised by [[Yorkshire Wildlife Trust]].<ref>{{cite web |title=Giving peat a(nother) chance {{!}} Yorkshire Wildlife Trust |url=https://www.ywt.org.uk/news/giving-peat-another-chance |access-date=14 January 2021 |website=ywt.org.uk|date=5 January 2021 }}</ref> ====Northern Ireland==== In [[Northern Ireland]], there is small-scale domestic turf cutting in rural areas, but areas of bogs have been diminished because of changes in agriculture. In response, [[afforestation]] has seen the establishment of tentative steps towards conservation such as [[Peatlands Park]], [[County Armagh]] which is an [[Area of Special Scientific Interest]].<ref>{{cite web |title=Peatlands Park ASSI |url=http://www.wonderfulni.info/protected_areas_home/new_assi_landing_page/county_armagh-2/peatlands_park_assi.htm |access-date=14 August 2010 |work=NI Environment Agency}}{{Dead link|date=May 2020|bot=InternetArchiveBot|fix-attempted=yes}}</ref> ====Scotland==== [[File:Peat-Stack in Ness, Outer Hebrides, Scotland.jpg|thumb|A peat stack in [[Ness, Western Isles|Ness]] on the [[Isle of Lewis]] ([[Scotland]])]] Some [[Scotch whisky]] distilleries, such as those on [[Islay]], use peat fires to dry malted [[barley]]. The drying process takes about 30 hours. This gives the whiskies a distinctive smoky flavour, often called "peatiness".<ref>{{cite web |title=Peat and Its Significance in Whisky |url=http://www.whisky.com/information/knowledge/tasting/flavour/peat-and-its-significance-in-whisky.html |access-date=25 October 2015}}</ref>{{Better source needed|reason=need more recent or change sentence to past tense|date=January 2022}} The peatiness, or degree of peat flavour, of a whisky is calculated in [[Parts-per notation#ppm|ppm]] of [[phenol]]. Normal Highland whiskies have a peat level of up to 30 ppm, and the whiskies on Islay usually have up to 50 ppm. In rare types like the [[Bruichladdich distillery|Octomore]],<ref>{{cite web |title=Octomore 5 Years 03.1 |url=http://www.whisky.com/whisky-database/bottle-search/details/fdb/Bottles/Details/octomore-031.html |access-date=25 October 2015}}</ref> the whisky can have more than 100 ppm of phenol. Scotch Ales can also use peat-roasted malt, imparting a similar smoked flavor. Because they are easily compressed under minimal weight, peat deposits pose significant difficulties for building structures, roads and railways. When the [[West Highland Line|West Highland railway line]] was constructed across [[Rannoch Moor]] in western Scotland, its builders had to float the tracks on a multi-thousand-ton mattress of tree roots, brushwood, earth and ash. ==== Wales ==== Wales has over 70,000 hectares of peatlands. Most of it is blanket peat bog in the highlands, but there are a few hundred hectares of peatland in lowland areas.<ref>{{Cite web |title=Welsh Peatland Sustainable Management Scheme (SMS) Project |url=https://www.nationaltrust.org.uk/abergwesyn-common/features/welsh-peatland-sustainable-management-scheme-sms-project |access-date=2022-09-06 |website=National Trust |language=en}}</ref> Some peatland areas in Wales are in poor condition. In 2020, the Welsh Government established a five-year peatland restoration initiative, which will be implemented by [[Natural Resources Wales]] (NRW).<ref>{{Cite web |title=Natural Resources Wales / The National Peatland Action Programme |url=https://naturalresources.wales/evidence-and-data/maps/the-national-peatland-action-programme/?lang=en |access-date=2022-09-06 |website=naturalresources.wales |language=en-gb}}</ref> ===Canada=== There are 294 million acres of peatland in Canada, with approximately 43,500 acres in production and another 34,500 acres involved in past production. The current and past acreage in production amounts to 0.03 percent of Canada's peatland.<ref>{{Cite journal |last=Altland |first=James |date=March 2024 |title=Peat industry confusion: The blurring of two separate issues. |journal=GPN Greenhouse Product News |volume=34 |issue=3 |pages=10}}</ref> Canada is the top exporter of peat by value. In 2021, top exporters of peat (including peat litter), whether or not agglomerated, were Canada ($580,591.39K, 1,643,950,000 kg), European Union ($445,304.42K, 2,362,280,000 kg), Latvia ($275,459.14K, 2,184,860,000 kg), Netherlands ($235,250.84K, 1,312,850,000 kg), Germany ($223,414.66K, 1,721,170,000 kg).<ref>{{cite web |title=Peat; (including peat litter), whether or not agglomerated exports by country in 2021 |url=https://wits.worldbank.org/trade/comtrade/en/country/ALL/year/2021/tradeflow/Exports/partner/WLD/product/270300 |access-date=19 May 2022 |website=WITS – World Integrated Solution |publisher=World Bank |ref=58}}</ref>
Summary:
Please note that all contributions to Niidae Wiki may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here.
You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see
Encyclopedia:Copyrights
for details).
Do not submit copyrighted work without permission!
Cancel
Editing help
(opens in new window)
Search
Search
Editing
Peat
(section)
Add topic