Assertion: biodegradable plastic | /r/HasProperty | caused methane emissions
Facets:
Source sentences:
text: If the plastic is incinerated, it increases carbon emissions; if it is placed in a landfill, it becomes a carbon sink although biodegradable plastics have caused methane emissions.  
text: If the plastic is incinerated, it increases carbon emissions; if it is placed in a landfill, it becomes a carbon sink, although biodegradable plastics have caused methane emissions.